[clang] [clang][Lex] Fix crash on pragma annotations in preprocessor expressions (PR #232413)

[Chen Miao via cfe-commits]

ChenMiaoi wrote:

> Yes, from what I saw recently we’re for some reason really bad at checking that something is _actually_ an identifier before we attempt to treat it like one all over the pragma code.
> 
> @ChenMiaoi was working on something similar to this; I don’t know if their patches cover this or not

It looks like this is another code path. When working on my fixes, I hadn't considered that directly calling `getIdentifierInfo()` in `EvaluateValue()` could also cause this issue. Yes, it's the same kind of problem, but on a different path that my current patches don't cover.

https://github.com/llvm/llvm-project/pull/232413