This is a reland of 7c80f9ce with fixed restore
of system stack pointer in the tests.

Original change's description:
> Abstract some stack slot copies through a macro assembler function. This
> eliminates some non-paired stack operations.
>
> This is a reland of 1cc93be0 with
> additional tests, originally reviewed on
> https://chromium-review.googlesource.com/685238 and reverted due to an
> unrelated intermittent x64 failure.
>
> Bug: v8:6644
> Change-Id: If22b359dbda4bab1cb83cd8c44a2af5801012c37
> Reviewed-on: https://chromium-review.googlesource.com/707247
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
> Cr-Commit-Position: refs/heads/master@{#48419}

Bug: v8:6644
Change-Id: Ie8b45c73acc13df36c978a9ae4bee77082cb7c8d
Reviewed-on: https://chromium-review.googlesource.com/709515Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
Cr-Commit-Position: refs/heads/master@{#48449}