[llvm] [InstCombine] Fold more 'fcmp' 'select' instrs idioms into 'fabs' (PR #83381)

[Matt Arsenault via llvm-commits]

arsenm wrote:

One annoying bit about handling this as a parameter attribute is we can't attach the same to other arbitrary sources (e.g. load) which should behave exactly the same. We would need another mirror metadata 

https://github.com/llvm/llvm-project/pull/83381