Revert of [runtime] Add fast-paths for common conversion methods (patchset #1 id:1 of https://codereview.chromium.org/2587013002/ )

Reason for revert:
breaks mips port: http://build.chromium.org/p/client.v8.ports/builders/V8%20Mips%20-%20builder/builds/6131

Original issue's description:
> [runtime] Add fast-paths for common conversion methods
>
> Add inlineable fast-paths for Object::ToPropertyKey, Object::ToLength and
> Object::ToIndex for the most common argument types.
>
> BUG=
>
> Review-Url: https://codereview.chromium.org/2587013002
> Cr-Commit-Position: refs/heads/master@{#41839}
> Committed: https://chromium.googlesource.com/v8/v8/+/d173807b9d8cb3c4cc4ee9c94c5cc960224b2c40

TBR=jgruber@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review-Url: https://codereview.chromium.org/2587373002
Cr-Commit-Position: refs/heads/master@{#41845}