[llvm] [LV] Make ScalarEpilogue a LoopVectorizeHint (PR #160125)

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

> as it is really a kind of hint that's dependent on the user's preferences

Aren't loop hints for loop pragmas etc? I don't think the user can control whether or not a scalar epilogue is emitted on a loop by loop basis. `-prefer-predicate-over-epilogue` is more of a TTI override

https://github.com/llvm/llvm-project/pull/160125