Now ResourceConstraints::ConfigureDefaults sets the heap limit to 4GB
if the physical memory size is greater or equal to 16GB on 64-bit
platforms.

This CL also adds tests for configuring heap limits from the physical
memory size.

Bug: chromium:1045034
Change-Id: If0d5a237b2db31309a9a2a6456d950ef70dc71af
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2043833
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66174}