Compute the Review Bot configuration page data in Python.

Review Request #12384 — Created June 17, 2022 and submitted — Latest diff uploaded




This updates ConfigureView to build most of the page state needed for
the configure page. This is less messy than doing it in the template,
more expandable, and allows us to reuse some state computation that
already existed on the Python side.

In the process, we get to remove the staticfiles template tag, which
doesn't exist on Django 3.2, and a bunch of tabs-vs-spaces issues have
been cleaned up.

Successfully configured Review Bot, changing broker URL settings and
seeing new broker status information. Also verified that the user shown
for Review Bot had all the correct information.