Revert of [turbofan] Use PlainPrimitiveToNumber whenever possible. (patchset #1 id:1 of https://codereview.chromium.org/852763002/)

Reason for revert:
Tanks performance of SQLite and towers.c.

Original issue's description:
> [turbofan] Use PlainPrimitiveToNumber whenever possible.
>
> TEST=cctest,unittests
> R=jarin@chromium.org
>
> Committed: https://crrev.com/1a5db24e6bf831e61e3f4aa0c252f77e48c3689c
> Cr-Commit-Position: refs/heads/master@{#26071}

TBR=jarin@chromium.org,dcarney@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/852153003

Cr-Commit-Position: refs/heads/master@{#26078}