[clang] No longer add enumeration constants to the wrong scope (PR #134998)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> It's not clear to me why the example in the PR description should be rejected, given https://eel.is/c++draft/dcl.enum#12.sentence-1. I also don't see a clear consensus on CWG reflector to determine whether this change moves us in the right direction. Do we have to change status quo before CWG revisits [CWG1485](https://cplusplus.github.io/CWG/issues/1485.html)?

I asked on the Core reflectors whether that direction is still one the committee thinks makes sense, the feedback so far as been roughly "maybe something close to it". So I'm waiting for the discussion to die down there to see if there's some agreement on a path forward.

https://github.com/llvm/llvm-project/pull/134998