[lldb-dap] Fix URL label and error code in DAPError (#145010)

This patch fixes some problems in DAPerror class (unnecessary copy in
ctor and typo in getUrlLabel function). During patch testing I found
flaky test TestDAP_server.test_server_interrupt (at least 1 fail on 50
runs). Looks like this problem is caused by data race between main and
event handler threads. Terminated event can be sent from Disconnect
function and event handler. However, only event handler sends exit
event. Also, after disconnecting, socket will be closed, so sometimes
sending event fails with "write failed: transport IO object invalid"
error. I tried to fix this problem by adding a wait for events thread
after disconnecting.

Failed log example:
```log
1750366596.399511337 lldb-dap server shutdown requested, disconnecting remaining clients...
1750366596.406297684 (client_0) <-- {"body":{"$__lldb_statistics":{"commands":"{}","memory":"{\"strings\":{\"bytesTotal\":2949120,\"bytesUnused\":1825545,\"bytesUsed\":1123575}}","plugins":"{\"abi\":[{\"enabled\":true,\"name\":\"SysV-arm64\"},{\"enabled\":true,\"name\":\"ABIMacOSX_arm64\"},{\"enabled\":true,\"name\":\"SysV-arm\"},{\"enabled\":true,\"name\":\"macosx-arm\"},{\"enabled\":true,\"name\":\"sysv-hexagon\"},{\"enabled\":true,\"name\":\"sysv-loongarch\"},{\"enabled\":true,\"name\":\"sysv-mips\"},{\"enabled\":true,\"name\":\"sysv-mips64\"},{\"enabled\":true,\"name\":\"sysv-msp430\"},{\"enabled\":true,\"name\":\"sysv-ppc\"},{\"enabled\":true,\"name\":\"sysv-ppc64\"},{\"enabled\":true,\"name\":\"sysv-riscv\"},{\"enabled\":true,\"name\":\"sysv-s390x\"},{\"enabled\":true,\"name\":\"abi.macosx-i386\"},{\"enabled\":true,\"name\":\"sysv-i386\"},{\"enabled\":true,\"name\":\"sysv-x86_64\"},{\"enabled\":true,\"name\":\"windows-x86_64\"}],\"architecture\":[{\"enabled\":true,\"name\":\"arm\"},{\"enabled\":true,\"name\":\"mips\"},{\"enabled\":true,\"name\":\"ppc64\"},{\"enabled\":true,\"name\":\"aarch64\"}],\"disassembler\":[{\"enabled\":true,\"name\":\"llvm-mc\"}],\"dynamic-loader\":[{\"enabled\":true,\"name\":\"darwin-kernel\"},{\"enabled\":true,\"name\":\"freebsd-kernel\"},{\"enabled\":true,\"name\":\"macosx-dyld\"},{\"enabled\":true,\"name\":\"macos-dyld\"},{\"enabled\":true,\"name\":\"posix-dyld\"},{\"enabled\":true,\"name\":\"static\"},{\"enabled\":true,\"name\":\"hexagon-dyld\"},{\"enabled\":true,\"name\":\"windows-dyld\"},{\"enabled\":true,\"name\":\"wasm-dyld\"}],\"emulate-instruction\":[{\"enabled\":true,\"name\":\"arm\"},{\"enabled\":true,\"name\":\"arm64\"},{\"enabled\":true,\"name\":\"LoongArch\"},{\"enabled\":true,\"name\":\"mips32\"},{\"enabled\":true,\"name\":\"mips64\"},{\"enabled\":true,\"name\":\"ppc64\"},{\"enabled\":true,\"name\":\"riscv\"}],\"instrumentation-runtime\":[{\"enabled\":true,\"name\":\"AddressSanitizer\"},{\"enabled\":true,\"name\":\"Libsanitizers-ASan\"},{\"enabled\":true,\"name\":\"MainThreadChecker\"},{\"enabled\":true,\"name\":\"ThreadSanitizer\"},{\"enabled\":true,\"name\":\"UndefinedBehaviorSanitizer\"}],\"jit-loader\":[{\"enabled\":true,\"name\":\"gdb\"}],\"language\":[{\"enabled\":true,\"name\":\"cplusplus\"},{\"enabled\":true,\"name\":\"objc\"},{\"enabled\":true,\"name\":\"objcplusplus\"}],\"language-runtime\":[{\"enabled\":true,\"name\":\"itanium\"},{\"enabled\":true,\"name\":\"apple-objc-v2\"},{\"enabled\":true,\"name\":\"apple-objc-v1\"},{\"enabled\":true,\"name\":\"gnustep-objc-libobjc2\"}],\"memory-history\":[{\"enabled\":true,\"name\":\"asan\"}],\"object-container\":[{\"enabled\":true,\"name\":\"bsd-archive\"},{\"enabled\":true,\"name\":\"mach-o\"},{\"enabled\":true,\"name\":\"mach-o-fileset\"}],\"object-file\":[{\"enabled\":true,\"name\":\"breakpad\"},{\"enabled\":true,\"name\":\"COFF\"},{\"enabled\":true,\"name\":\"elf\"},{\"enabled\":true,\"name\":\"JSON\"},{\"enabled\":true,\"name\":\"mach-o\"},{\"enabled\":true,\"name\":\"minidump\"},{\"enabled\":true,\"name\":\"pdb\"},{\"enabled\":true,\"name\":\"pe-coff\"},{\"enabled\":true,\"name\":\"xcoff\"},{\"enabled\":true,\"name\":\"wasm\"}],\"operating-system\":[{\"enabled\":true,\"name\":\"python\"}],\"platform\":[{\"enabled\":true,\"name\":\"remote-AIX\"},{\"enabled\":true,\"name\":\"remote-linux\"},{\"enabled\":true,\"name\":\"remote-android\"},{\"enabled\":true,\"name\":\"remote-freebsd\"},{\"enabled\":true,\"name\":\"remote-gdb-server\"},{\"enabled\":true,\"name\":\"darwin\"},{\"enabled\":true,\"name\":\"remote-ios\"},{\"enabled\":true,\"name\":\"remote-macosx\"},{\"enabled\":true,\"name\":\"host\"},{\"enabled\":true,\"name\":\"remote-netbsd\"},{\"enabled\":true,\"name\":\"remote-openbsd\"},{\"enabled\":true,\"name\":\"qemu-user\"},{\"enabled\":true,\"name\":\"remote-windows\"}],\"process\":[{\"enabled\":true,\"name\":\"ScriptedProcess\"},{\"enabled\":true,\"name\":\"elf-core\"},{\"enabled\":true,\"name\":\"mach-o-core\"},{\"enabled\":true,\"name\":\"minidump\"},{\"enabled\":true,\"name\":\"gdb-remote\"}],\"register-type-builder\":[{\"enabled\":true,\"name\":\"register-types-clang\"}],\"repl\":[{\"enabled\":true,\"name\":\"ClangREPL\"}],\"script-interpreter\":[{\"enabled\":true,\"name\":\"script-none\"},{\"enabled\":true,\"name\":\"script-python\"}],\"scripted-interface\":[{\"enabled\":true,\"name\":\"OperatingSystemPythonInterface\"},{\"enabled\":true,\"name\":\"ScriptedPlatformPythonInterface\"},{\"enabled\":true,\"name\":\"ScriptedProcessPythonInterface\"},{\"enabled\":true,\"name\":\"ScriptedStopHookPythonInterface\"},{\"enabled\":true,\"name\":\"ScriptedThreadPlanPythonInterface\"}],\"structured-data\":[{\"enabled\":true,\"name\":\"darwin-log\"}],\"symbol-file\":[{\"enabled\":true,\"name\":\"breakpad\"},{\"enabled\":true,\"name\":\"CTF\"},{\"enabled\":true,\"name\":\"dwarf\"},{\"enabled\":true,\"name\":\"dwarf-debugmap\"},{\"enabled\":true,\"name\":\"JSON\"},{\"enabled\":true,\"name\":\"native-pdb\"},{\"enabled\":true,\"name\":\"symtab\"}],\"symbol-locator\":[{\"enabled\":true,\"name\":\"debuginfod\"},{\"enabled\":true,\"name\":\"Default\"}],\"symbol-vendor\":[{\"enabled\":true,\"name\":\"ELF\"},{\"enabled\":true,\"name\":\"PE-COFF\"},{\"enabled\":true,\"name\":\"WASM\"}],\"system-runtime\":[{\"enabled\":true,\"name\":\"systemruntime-macosx\"}],\"trace-exporter\":[{\"enabled\":true,\"name\":\"ctf\"}],\"type-system\":[{\"enabled\":true,\"name\":\"clang\"}],\"unwind-assembly\":[{\"enabled\":true,\"name\":\"inst-emulation\"},{\"enabled\":true,\"name\":\"x86\"}]}","targets":"[{\"breakpoints\":[{\"details\":{\"Breakpoint\":{\"BKPTOptions\":{\"AutoContinue\":false,\"ConditionText\":\"\",\"EnabledState\":true,\"IgnoreCount\":0,\"OneShotState\":false},\"BKPTResolver\":{\"Options\":{\"Column\":0,\"Exact\":false,\"FileName\":\"/home/sergei/llvm-project/lldb/test/API/tools/lldb-dap/server/main.c\",\"Inlines\":true,\"LineNumber\":4,\"Offset\":0,\"SkipPrologue\":true},\"Type\":\"FileAndLine\"},\"Hardware\":false,\"Names\":[\"dap\"],\"SearchFilter\":{\"Options\":{},\"Type\":\"Unconstrained\"}}},\"hitCount\":1,\"id\":1,\"internal\":false,\"numLocations\":1,\"numResolvedLocations\":1,\"resolveTime\":0.064788999999999999},{\"details\":{\"Breakpoint\":{\"BKPTOptions\":{\"AutoContinue\":false,\"ConditionText\":\"\",\"EnabledState\":true,\"IgnoreCount\":0,\"OneShotState\":false},\"BKPTResolver\":{\"Options\":{\"Language\":\"c\",\"NameMask\":[4,4,4,4,4,4],\"Offset\":0,\"SkipPrologue\":false,\"SymbolNames\":[\"_dl_debug_state\",\"rtld_db_dlactivity\",\"__dl_rtld_db_dlactivity\",\"r_debug_state\",\"_r_debug_state\",\"_rtld_debug_state\"]},\"Type\":\"SymbolName\"},\"Hardware\":false,\"SearchFilter\":{\"Options\":{\"ModuleList\":[\"/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2\"]},\"Type\":\"Modules\"}}},\"hitCount\":2,\"id\":-1,\"internal\":true,\"kindDescription\":\"shared-library-event\",\"numLocations\":1,\"numResolvedLocations\":1,\"resolveTime\":0.00027700000000000001}],\"dyldPluginName\":\"posix-dyld\",\"expressionEvaluation\":{\"failures\":0,\"successes\":0},\"firstStopTime\":0.081890439999999995,\"frameVariable\":{\"failures\":0,\"successes\":0},\"launchOrAttachTime\":0.044839855999999997,\"moduleIdentifiers\":[140296113373488,140296115439216,140296116813568,140295710837504,140295643597696,140294502747184,140294972632368],\"signals\":[{\"SIGSTOP\":1}],\"sourceMapDeduceCount\":0,\"sourceRealpathAttemptCount\":0,\"sourceRealpathCompatibleCount\":0,\"stopCount\":7,\"summaryProviderStatistics\":[],\"targetCreateTime\":0.000736,\"totalBreakpointResolveTime\":0.065065999999999999,\"totalSharedLibraryEventHitCount\":2}]","totalDebugInfoByteSize":5107143,"totalDebugInfoEnabled":4,"totalDebugInfoIndexLoadedFromCache":0,"totalDebugInfoIndexSavedToCache":0,"totalDebugInfoIndexTime":0.183807,"totalDebugInfoParseTime":1.2240820000000001,"totalModuleCount":7,"totalModuleCountHasDebugInfo":4,"totalModuleCountWithIncompleteTypes":0,"totalModuleCountWithVariableErrors":0,"totalSymbolLocatorTime":"{\"Default\":0.0054260000000000003,\"debuginfod\":6.999999999999999e-06}","totalSymbolTableIndexTime":0.014254000000000001,"totalSymbolTableParseTime":0.099803000000000003,"totalSymbolTableStripped":0,"totalSymbolTableSymbolCount":23098,"totalSymbolTablesLoaded":7,"totalSymbolTablesLoadedFromCache":0,"totalSymbolTablesSavedToCache":0}},"event":"terminated","seq":0,"type":"event"}
1750366596.406688452 (client_0) write failed: transport IO object invalid
1750366596.406724215 (client_0) write failed: transport IO object invalid
1750366596.842197657 (client_0) client disconnected
```