Revert of [runtime] Replace global object link with native context link in all contexts. (patchset #3 id:40001 of https://codereview.chromium.org/1480003002/ )

Reason for revert:
[Sheriff] Breaks:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20nosnap/builds/5472

Original issue's description:
> [runtime] Replace global object link with native context link in all contexts.
>
> Previously all contexts had a link to the global object, but what is
> required in most cases (except for the global load, store and delete
> case) is the native context.
>
> This also removes the second dummy global object that was still linked
> to every native context. We will add a different mechanism to ensure
> that builtins do not pollute the actual global object during
> bootstrapping.
>
> Drive-by-fix: Unify some MacroAssembler magic and drop obsolete stuff.
>
> R=yangguo@chromium.org
>
> Committed: https://crrev.com/d290f204938295bfecc5c8e645ccfcff6e80ddb8
> Cr-Commit-Position: refs/heads/master@{#32375}

TBR=yangguo@chromium.org,mstarzinger@chromium.org,bmeurer@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1478303002

Cr-Commit-Position: refs/heads/master@{#32377}