Added missing available app in migrations test case

In some test combinations, having contrib.auth available but not
contrib.contenttypes can produce failures while creating permissions.
Fixed #23444 -- Deprecated django.contrib.admin.helpers.InlineAdminForm.original_content_type_id
Fixed #23702 -- Fixed adding an explicit id field on SQLite.

Thanks gavinwahl for the report.
Fixed #23707 -- Prevented discovery of duplicated tests
Fixed typo in docs/ref/request-response.txt
Fixed #23618 -- Allowed apps with no models to still have migrations

Basically a4737bf6ae reapplied.
Updated gis_migrations tests
Fixed #23652 -- Restored database name after destroying test database

Thanks Bjarkias for the report.
Removed unused import
Fixed versionchanged indentation in topics/testing/advanced.txt.
Replaced dead links to python-distribute.org.
Removed simplejson inventory file from docs/conf.py.
Fixed #23446 -- Officially recommended mysqlclient as MySQL driver

Thanks Corey Farwell for the report and Tim Graham for the review.
Thanks also to Inada Naoki for creating and maintaining mysqlclient.
Fixed documentation of make_password kwargs.
Fixed #23699 -- Prevented flush from loading initial data for apps with migrations.
Forwardported release note for refs #23621.
Removed some commented code in the forms Media class.
Fixed #22879 -- Intercept errors coming from cursor.__next__()
Fixed #23717 -- Fixed makemessages crash when STATIC_ROOT=None
Fixed typo in MySQL backend doctring

Thanks CHI Cheng for the report.