A pointer-compressed heap has the same heap limit heuristics as a 32-bit
heap. Specifically, the heap limit is restricted to 1GB due to scarce
virtual addresses space on 32-bit platforms. That limitation does not
apply for pointer-compressed heaps which can use 4GB.

This CL changes the heap limit computation to use system the pointer
size instead of the tagged pointer size. Note that the young generation
limit continues to use the tagged pointer size.

Bug: chromium:1045034
Change-Id: I9d5bb818c32a82322476e9c97feee331400ebe0f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2042102Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66159}