[clang] [llvm] [AArch64] Decouple feature dependency expansion. (PR #94279)

[Alexandros Lamprineas via cfe-commits]

labrinea wrote:

> Not supporting "neon" as a name would seem like a mistake if it was removed, but I don't believe this patch does that.

It does 

https://github.com/llvm/llvm-project/pull/94279