[VE] Change the way to lower selectcc

Change to use VEISD::CMPI/CMPU/CMPF/CMPQ and VEISD::CMOV in combineSelectCC
for better optimization.  Support VEISD::CMPI/CMPU in combineTRUNCATE also
to optimize truncate.  Remove obsolete lower patterns from VEInstrInfo.td.
Update regression tests also.

Reviewed By: efocht

Differential Revision: https://reviews.llvm.org/D136049