[clang] [Clang] Add queryable feature 'boolean_vectors' for SIMD masks (PR #154227)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> I clicked accept, but not sure I'm super in favor of the name? Maybe see if folks will bikeshed it for you? I'm a bit concerned it is too close to other things (vector is ambiguous of course).
> 
> Maybe:
> 
> `boolean_gnu_vector_type` and `boolean_ext_vector_type`
> 
> WDYT?

Yeah, I was wondering about that. I don't think we support the GNU vectors to be boolean yet so it can be a little confusing. Maybe just `ext_vector_type_boolean`? 

https://github.com/llvm/llvm-project/pull/154227