[clang] [clang] Add clang::debug_info_type attribute for bitfields (PR #69104)

[via cfe-commits]

philnik777 wrote:

Wouldn't it be better to go the other way around? i.e. have a `[[clang::compressed_bitfield]]` (or whatever) which influences the ABI, so it's possible to do stuff like
```c++
[[clang::compressed_bitfield]] bool IsSomething : 1;
[[clang::compressed_bitfield]] MyEnum Whatever : 3;
[[clang::compressed_bitfield]] int MoreStuff : 4;
```
which the current approach doesn't allow.

https://github.com/llvm/llvm-project/pull/69104