Following the disassembler, break up these opcodes into a separate
function.  The decoding follows the disassembler quite closely, except
in places where the simulator implementation grouped opcodes together to
share code.

Code is all copy paste, more clean ups to follow.

Bug: v8:11074
Change-Id: I426d3542715a27e7c3a49e2118efebe595c7baa4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2509091
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70933}