Revert of Make V8 extras a separate type of native (patchset #4 id:60001 of https://codereview.chromium.org/1129743003/)

Reason for revert:
https://build.chromium.org/p/client.v8/builders/V8-Blink%20Linux%2064%20%28dbg%29/builds/2745

Original issue's description:
> Make V8 extras a separate type of native
>
> Instead of making them an extra option that gets passed in and compiled
> at the end of the natives file for a given run of js2c, we now make them a
> separate run of js2c with a separate natives file output.
>
> This natives file output is then compiled in the bootstrapper. It is not part
> of the snapshot (yet), but instead is treated similar to the experimental
> natives, just without any of the complexity that comes from tieing the
> behavior to flags. We also don't add counterparts to
> InitializeExperimentalGlobal and InstallExperimentalNativeFunctions, yet.
>
> R=yangguo@chromium.org, jochen@chromium.org
> BUG=
>
> Committed: https://crrev.com/c93aff4ac63ad9ffb6318e750335208de32b7902
> Cr-Commit-Position: refs/heads/master@{#28296}

TBR=jochen@chromium.org,yangguo@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/1131903002

Cr-Commit-Position: refs/heads/master@{#28299}