[clang] [Clang][Diagnostics] Update select uses in DiagnosticXKinds.td to use enum_select (PR #130868)

[Erich Keane via cfe-commits]

erichkeane wrote:

> I was wondering if it was okay for a replacement since the names of the CommandTraits options are the same. Also would a select with only 1 use (with a magic number) be up for replacement?

I'll check out the review.  As far as this CommandTraits one, it probably is not a good candidate.  There is already an enum for it that is stored in the AST.  

As far as 1 use: Yes, if it has 1 use with a magic number, that is a perfectly reasonable thing to replace with an enum_select.

https://github.com/llvm/llvm-project/pull/130868