JIT today's new _imm ops

- Add YmmOrLabel struct to represent the concept that many
  x86 instructions can take a final argument as either a
  register or memory address, and that they all handle them
  the same way.
- Convert existing overloads like vmulps() to use YmmOrLabel.
- upgrade some other instructions to take YmmOrLabel
- use them to implement today's new _imm ops

This feels like a good spot for implicit constructors, no?

Change-Id: I435028acc3fbfcc16f634cfccc98fe38bbce9d19
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263207
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed