[X86] Teach the assembler parser to handle a '*' between segment register and...

[X86] Teach the assembler parser to handle a '*' between segment register and base/index/displacement part of an address

A '*' after the segment is equivalent to a '*' before the segment register. To make the AsmMatcher table work we need to place the '*' token into the operand vector before the full memory operand. To accomplish this I've modified some portions of operand parsing to expose the operand vector to ParseATTOperand so that the token can be pushed to the vector after parsing the segment register and before creating the memory operand using that segment register.

Fixes PR46879

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D84895