[compiler-rt] [compiler-rt][AArch64] Rewrite SME routines to all use __aarch64_cpu_features. (PR #119414)

[Amara Emerson via llvm-commits]

aemerson wrote:

> I'm not sure we want this on Darwin and maybe Fuchsia platforms, since it would require calling `__init_cpu_features_resolver` to initialize `__aarch64_cpu_features`. On some platforms that happens automatically via an `__attribute__((constructor))` function, but Darwin and Fuchsia don't, and instead rely on an FMV resolver triggering it.
> 
> cc @aemerson

There's no immediate concern for Darwin because we have our own parallel implementations of the SME runtime routines.

https://github.com/llvm/llvm-project/pull/119414