[X86] Convert integer _mm_reduce_* intrinsics to emit llvm.reduction intrinsics (PR47506)

Emit the equivalent integer reduction intrinsics in IR instead of expanding to shuffle+arithmetic sequences.

The fadd/fmul reductions might be trickier as they assume a similar bisection reduction while the generic intrinsics assume a sequential reduction (intel docs are ambiguous on the correct approach) - I'm not sure if we want to always tag them with reassoc? Anyway, that issue can wait until a separate fp patch along with the fmin/fmax reductions.

Differential Revision: https://reviews.llvm.org/D87604