[InstCombine] `vector_reduce_umax(?ext(<n x i1>))` --> `?ext(vector_reduce_or(<n x i1>))` (PR51259)

Alive2 agrees:
https://alive2.llvm.org/ce/z/NbBaeT (self)
https://alive2.llvm.org/ce/z/iEaig4 (zext)
https://alive2.llvm.org/ce/z/meGb3y (sext)

We already handle `vector_reduce_and(<n x i1>)`,
so let's just combine into the already-handled pattern
and let the existing fold do the rest.