[X86][AVX] Push sign extensions of comparison bool results through bitops (PR42025)

As discussed on PR42025, with more complex boolean math we can end up with many truncations/extensions of the comparison results through each bitop.

This patch handles the cases introduced in combineBitcastvxi1 by pushing the sign extension through the AND/OR/XOR ops so its just the original SETCC ops that gets extended.

Differential Revision: https://reviews.llvm.org/D68226

llvm-svn: 373834