[llvm] [AArch64]: Refactor target parser to use BitVector. (PR #65423)

[David Spickett via llvm-commits]

DavidSpickett wrote:

With just the bitvector change this is fine.

I don't disagree with splitting the test files but it should be in its own commit/PR.

https://github.com/llvm/llvm-project/pull/65423