When encountering a LoadStackPointer input to a comparison, generate a register
LocationOperand that points to the stack pointer. This can avoid unnecessary
spilling of the stack pointer.

Since sp is a special register for arm64, we need to add a mechanism to print
its name in RegisterConfiguration.

This is a port of https://chromium-review.googlesource.com/1055568 that made
the same change for arm.

It also ports the tests added in
https://chromium-review.googlesource.com/1099068 to arm and arm64.

Bug: v8:7844
Change-Id: I5adc672ff877b9888ef755e8e60e4eabbc61061b
Reviewed-on: https://chromium-review.googlesource.com/1107810Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#53889}