[clang] [compiler-rt] [llvm] [X86] Sync multiversion features with libgcc and refactor internal feature tables (PR #168750)

[Mikołaj Piróg via cfe-commits]

mikolaj-pirog wrote:

These changes (sync with libgcc and refactor) could be treated as a separate, but I opted to do them in one go, since if I did update before refactor I would have to proceed with hacky way of maintaining the ordering only to remove it immediately later -- the other way around I would be encoding wrong bit values of features. If need be I can split to refactor and update part.


https://github.com/llvm/llvm-project/pull/168750