Revert "Move gmerge_binhost logic to Chromite"

This reverts commit 8fd60b10cef9cfa71c463442d136e495166bd025.

Reason for revert: Broke release builders: http://b/338512093#comment17

Original change's description:
> Move gmerge_binhost logic to Chromite
>
> Extract the logic to update a gmerge binhost into Chromite, since it's
> imported by strip_package.py and we don't want Chromite importing
> modules from platform. And add a unit test to prove it works.
>
> We leave the Builder here since that's not needed in Chromite.
>
> BUG=b:338512093
> TEST=./builer_test.py
>
> Cq-Depend: chromium:5531182
> Change-Id: I7ac056e1f27af7bb1e53701165a0c865a1d3be9a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/5530710
> Tested-by: Tim Bain <tbain@google.com>
> Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
> Reviewed-by: Jesse McGuire <jessemcguire@google.com>
> Commit-Queue: Tim Bain <tbain@google.com>

BUG=b:338512093

Change-Id: I6cc17f63be0eb0ca5805d835a40259a3d150089f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/5545057
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Jesse McGuire <jessemcguire@google.com>
Auto-Submit: Tim Bain <tbain@google.com>
Tested-by: Tim Bain <tbain@google.com>
Commit-Queue: Jesse McGuire <jessemcguire@google.com>
2 files changed