[llvm] [AArch64][AsmParser] Directives should clear transitively implied features (PR #106625)

[Sander de Smalen via llvm-commits]

================
@@ -6991,11 +6991,12 @@ bool AArch64AsmParser::parseDirectiveArch(SMLoc L) {
       if (Extension.Features.none())
----------------
sdesmalen-arm wrote:

Not caused by your patch, but if the Extension isn't found then that seems to be silently ignored.

That's even explicit in one of the tests directive-arch-negative.s:
```
// We silently ignore invalid features.
  .arch armv8+foo
  aese v0.8h, v1.8h
```

Should this actually result in a diagnostic?

https://github.com/llvm/llvm-project/pull/106625