[X86] Add full set of patterns for turning ceil/floor/trunc/rint/nearbyint into rndsc...

[X86] Add full set of patterns for turning ceil/floor/trunc/rint/nearbyint into rndscale with loads, broadcast, and masking.

This amounts to pretty ridiculous number of patterns. Ideally we'd canonicalize the X86ISD::VRNDSCALE earlier to reuse those patterns. I briefly looked into doing that, but some strict FP operations could still get converted to rint and nearbyint during isel. It's probably still worthwhile to look into. This patch is meant as a starting point to work from.

llvm-svn: 337234