This reverts commit 0f13273f.

Reason for revert: breaks codesearch recipes and autorollers

crbug.com/1298961

Original change's description:
> Add support for Gerrit topics in gclient syncs
>
>
> If the new flag "--download-topics" is specified with a "--patch-ref" then:
> * Finds the topic of the Gerrit change.
> * Finds all open changes in the same repo as the Gerrit change.
> * Cherrypicks all changes locally.
>
> This functionality can be used by developers and bots to apply all changes with the same topic in the checkout to be tested at the same time (similar to how Android's TreeHugger handles topics).
>
>
> Tested by:
>
> * Running the new unit test with `python gclient_scm_test.py GerritChangesTest.testDownloadsTopics` from the `tests/` directory.
>
> * Running an end-to-end test with `DEPOT_TOOLS_UPDATE=0 gclient sync --patch-ref "skia@d831da5b8ac2d257c5b0cf2ec6645a148f05e662:refs/changes/17/505217/2" --download-topics` in a skia checkout.
>
>
> Bug: chromium:1298922
> Change-Id: Ieace5e27fbc9c5d0ea90a037bf80a95062c1b164
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3444003
> Reviewed-by: Josip Sokcevic <sokcevic@google.com>
> Commit-Queue: Ravi Mistry <rmistry@chromium.org>

Bug: chromium:1298922
Bug: chromium:1298961
Change-Id: I88c56cd68372bad09b612de7de1a45f9a0c6c681
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3474793
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>