This is a reland of 7ae30cb7

Original change's description:
> [heap] Skip memory reducer on AdjustAmountOfExternalAllocateMemory
>
> V8 performs GC based on external memory limit. Additionally triggering
> memory reducing GCs may be problematic for large heaps and increases
> the chances of multiple V8 isolates performing GCs after
> IsolateInBackgroundNotification.
>
> Bug: chromium:1072746
>
> Change-Id: I7649a176504803ba666e6367b008593bbcfe6312
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2159488
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67398}

Bug: chromium:1072746
Tbr: mlippautz@chromium.org,hpayer@chromium.org
Change-Id: Ieccd77c868a8b5d5613e6c4b7e70fdb4bcff3044
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2165763Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67409}