[clang] [llvm] [AArch64][TargetParser] Split FMV and extensions (PR #92882)

[Tomas Matheson via cfe-commits]

tmatheson-arm wrote:

> Looking good Tomas and thanks for your effort to tidy things up. I know this is NFC, but can we rectify the implied features for rcpc2 and rcpc3 by adding rcpc-immo as shown here https://github.com/llvm/llvm-project/pull/92319/files#diff-0df0a19b911b768165642047ad84892b945f9e2e652f91e8d9ed911b21915ec4R488 ?

That would be better as a separate PR.

https://github.com/llvm/llvm-project/pull/92882