[llvm] [AArch64] Refactor redundant PTEST optimisations (NFC) (PR #87802)

[Momchil Velikov via llvm-commits]

momchil-velikov wrote:

https://github.com/llvm/llvm-project/pull/87802 and https://github.com/llvm/llvm-project/pull/81141 rebased on top of main, no longer descendants to the wide active lane mask patch (https://github.com/llvm/llvm-project/pull/81140)

https://github.com/llvm/llvm-project/pull/87802