[llvm] Add an all-in-one histogram intrinsic, along with lowering for AArch64 (PR #88106)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Looks good. Agree with proceeding with some of the FIXMEs.

https://github.com/llvm/llvm-project/pull/88106