[X86][CostModel] Bump the cost of vpermw/vpermt2b/vperm2w

[X86][CostModel] Bump the cost of vpermw/vpermt2b/vperm2w

vpermw is 2 uops. vpermt2b/vpermt2w are two shuffle uops and a port 015 uop. Weirdly vpermb is a single uop.

This patch bumps the cost to 2 for these operations. Maybe should go to 3 for the vpermt2*, but I've started conservative.

I've also removed a few entries that were now the same as earlier subtargets or that I didn't think we really did. Like I don't think we extend v32i8 to v32i16, shuffle, and then truncate.

Differential Revision: https://reviews.llvm.org/D79148