[clang] [llvm] [X86][AVX10] Remove EVEX512 and AVX10-256 implementations (PR #157034)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> Do we have any test coverage of the error messages if people use the old args and does it explain how they can fix it? Not sure how important it is given its still early days for avx10 but I imagine someone has already started using it......

Yes, we have reported warning in LLVM21 and have tests for it: https://github.com/llvm/llvm-project/pull/132542/files#diff-5f03b616b46b38c8f00da84c616bd5096df4ee66ecb9a7c20e980e4d0008f894R414

With this change, users will get an error like `error: unknown argument: '-mavx10.1-512'`

https://github.com/llvm/llvm-project/pull/157034