This will make it easier to call new or uncommon Gerrit APIs, without
needing to add dedicated methods for each one. This also makes it easier
to debug API calls by exposing the raw response data, which is often
processed or filtered in the existing wrapper methods.

BUG=1052179
R=linxinan@chromium.org

Change-Id: I0b594a9fdaabae4b0ebb379dc5473f4d6de67a13
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3235714
Auto-Submit: Michael Moss <mmoss@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Xinan Lin <linxinan@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@google.com>