Revert of [heap] Uncommit unused large object page memory. (patchset #13 id:230001 of https://codereview.chromium.org/2032393002/ )

Reason for revert:
Needs fixing of slot set.

Original issue's description:
> [heap] Uncommit unused large object page memory.
>
> As a first step I uncommit the memory on the main thread. Also to measure impact and stability of that optimization. In a follow-up CL, the uncommitting should be moved on the concurrent thread.
>
> BUG=
>
> Committed: https://crrev.com/d61a5c376ba51145dc4684e39d5d3a9ce75bcfa6
> Cr-Commit-Position: refs/heads/master@{#36763}

TBR=ulan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review-Url: https://codereview.chromium.org/2043263002
Cr-Commit-Position: refs/heads/master@{#36807}