Provide a global memory controller used to compute limits for combined
on-heap and embedder memory. The global controller uses the same
mechanism (gc speed, mutator speed) and growing factors as the regular
on-heap controller.

Rely on V8's mechanisms for configured state that stops shrinking the
limit.

Bug: chromium:948807
Change-Id: I3283a2c28e6ab889f8d2ad85c9b67b8f234b9900
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1619762
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61712}