[lldb] Make single-argument Address constructor explicit (NFC) (#189035)

This is to highlight places where we (probably unintentionally)
construct an `Address` object from an already resolved address, making
it unresolved again.
See the changes in `DynamicLoaderDarwin.cpp` for a quick example.

Also, use this constructor instead of `Address(lldb::addr_t file_addr,
const SectionList *section_list)` when `section_list` is `nullptr`.

GitOrigin-RevId: 22cfe6f39d432bd095e9a3638033f2bb99f83c8e