This validates that:
a) checked in generated files correspond to what lucicfg
   actually generates;
b) lucicfg is formatted
c) (same as before) configs are validated against respective
   LUCI services.

Change-Id: I727723beb4172c3dd265c4a4edbc2ecbfb479eb9
Bug: chromium:1204972
No-Try: True
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2867081
Commit-Queue: Andrii Shyshkalov <tandrii@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>