[X86] Try to avoid casts around logical vector ops recursively.

Currently PromoteMaskArithemtic only looks at a single operation to
skip casts. This means we miss cases where we combine multiple masks.

This patch updates PromoteMaskArithemtic to try to recursively promote
AND/XOR/AND nodes that terminate in truncates of the right size or
constant vectors.

Reviewers: craig.topper, RKSimon, spatel

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D72524