[X86] Auto upgrade old style VPCOM/VPCOMU intrinsics to generic integer comparisons

We were upgrading these to the new style VPCOM/VPCOMU intrinsics (which includes the condition code immediate), but we'll be getting rid of those shortly, so convert these to generics first.

This causes a couple of changes in the upgrade tests as signed/unsigned eq/ne are equivalent and we constant fold true/false codes, these changes are the same as what we already do for avx512 cmp/ucmp.

Noticed while cleaning up vector integer comparison costs for PR40376.

llvm-svn: 351690