[X86][MC] Support encoding/decoding for PUSHP/POPP (#73092)

A PUSH and its corresponding POP may be marked with a 1-bit Push-Pop Acceleration (PPX)
hint to indicate that the POP reads the value written by the PUSH from the stack. The PPX hint
is encoded by setting REX2.W = 1 and is applicable only to PUSH with opcode 0x50+rd and POP
with opcode 0x58+rd in the legacy space. It is not applicable to any other variants of PUSH and POP.