[clang] [llvm] [clang][DebugInfo] Emit unified (Itanium) mangled name to structor declarations (PR #154142)

[Michael Buch via cfe-commits]

Michael137 wrote:

Test failure is an XPASS in `TestExprDefinitionInDylib` because the LLDB `AsmLabel` now has a mangled name in it and the lookup by mangled name succeeds. Though it's technically not correct because we're not guaranteed to pick the right constructor variant (we probably just pick the first one we find). I'll un-XFAIL it here and it should be fixed by the [LLDB patch that I'll land at the same time as this PR](https://github.com/llvm/llvm-project/pull/149827)

https://github.com/llvm/llvm-project/pull/154142