[lldb-vscode] Consistently use return EXIT_SUCCESS and EXIT_FAILURE (NFC)

Consistently use return with EXIT_SUCCESS or EXIT_FAILURE instead of
mix-and-matching return, exit 0, 1 etc.

Differential revision: https://reviews.llvm.org/D99701

GitOrigin-RevId: 54c3c2e82874d8ee65b32f1f79bfd494b0551986
1 file changed