This CL implements all variants of CompareExchange on arm.

Implementing 64-bit CompareExchange on arm requires a lot of registers,
with the additional constraint that the low-word register of new_value
and result have to have an even register code, and that the corresponding
high-word registers have a register code that is by one higher than the
register code of the low-word register.

This register allocation is achieved by assigning fixed registers to
all values.

R=clemensb@chromium.org, v8-arm-ports@googlegroups.com

Bug: v8:10108
Change-Id: I2edfde15e80db0d45621a461793018d88e997431
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2172791
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67592}