[X86] Use some preprocessor macros to reduce the very similar repeated code in getVPTESTMOpc. NFCI

This function picks X86 opcode name based on type, masking,
and whether not a load or broadcast has been folded using multiple
switch statements. The contents of the switches mostly just vary in
a few characters in the instruction name. So use some macros to
build the instruction names to reduce the repetiveness.