This reverts commit ce23fd64.

Original change's description:
> [heap] Clean up Heap::ConfigureHeap
>
> This re-arranges the implementation of the function to make it more
> consistent. The only functional change is replacement of RoundUp with
> RoundDown, which makes more sense for the limits.
>
> Bug: v8:9306
> Change-Id: Id1d4bc6cc414e3618c3878de8cb87a9ed59711f5
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1643432
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#61997}

TBR=mlippautz@chromium.org,jgruber@chromium.org


Change-Id: I2352c1305ea3e617b32951e4b1aa871271800478
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1645330
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62008}