[llvm] [AArch64][FEAT_CMPBR] Codegen for Armv9.6-a compare-and-branch (PR #116465)

[Jon Roelofs via llvm-commits]

https://github.com/jroelofs approved this pull request.

Suggest adding a couple more tests, but otherwise LGTM.

https://github.com/llvm/llvm-project/pull/116465