This adds a parameter to bot_update.ensure_checkout that will cause
blamelist pins to be set for all of the repos whose revision is not
determined by DEPS files: the repo for the gitiles input, the repo for
each solution in the gclient config and any repos with the revision set
by the revisions field of the gclient config.

Bug: 1047893
Change-Id: Ie3eee41dbf15be014185b6f255ee3d4cfd40b4e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2293514
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>