[llvm] [ARM] Replace ABS and tABS machine nodes with custom lowering (PR #156717)

[via llvm-commits]

AZero13 wrote:

Anyway, the costs are fine and more accurate now. if we want to worry about cycles, that should be in another PR because I do not know how to do this without having it apply to all intrinsics that involve shifted operands. @davemgreen.

https://github.com/llvm/llvm-project/pull/156717