[InstCombine] `vector_reduce_smax(?ext(<n x i1>))` -->...

[InstCombine] `vector_reduce_smax(?ext(<n x i1>))` --> `?ext(vector_reduce_{and,or}(<n x i1>))` (PR51259)

Alive2 agrees:
https://alive2.llvm.org/ce/z/3oqir9 (self)
https://alive2.llvm.org/ce/z/6cuI5m (zext)
https://alive2.llvm.org/ce/z/4FL8rD (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.