[clang] [llvm] [clang][DebugInfo] Mark _BitInt's as reconstitutable when emitting -gsimple-template-names (PR #168383)

[David Blaikie via llvm-commits]

https://github.com/dwblaikie approved this pull request.

The changes to simple-template-names.cpp should, in some part of this series, end up in the cross-project-tests version of the test, so we test the full roundtrip.

Thanks so much for taking an interest in/improving simplified template names!

https://github.com/llvm/llvm-project/pull/168383