Change to use VEISD::CMOV in combineSelect for better optimization.
Support VEISD::CMOV in combineTRUNCATE also to optimize trancate.
Merge functions to handle condition codes to VE.h. And add basic
CMOV patterns to VEInstrInfo.td. Update regression tests also.
Reviewed By: efocht
Differential Revision: https://reviews.llvm.org/D135878