[clang] [compiler-rt] [llvm] [X86] Remove vector length (256 vs 512) distinction of AVX10 (PR #167736)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> There are still remnants of 256 vs 512 distinction, like defining `__AVX10_1_512__` and `FeatureAVX10_1_512` in the X86.td -- but I believe those should stay, for compatibility purposes, right?

Yes, please add tests for `-mattr=+avx10.1/2-512` in case we won't remove them by accident.

https://github.com/llvm/llvm-project/pull/167736