refs #17627.

Forward port of 666c12e5 from stable/1.8.x

Several issues resolved here, following from a report that a base_field
of GenericIpAddressField was failing.

We were using get_prep_value instead of get_db_prep_value in ArrayField
which was bypassing any extra modifications to the value being made in
the base field's get_db_prep_value. Changing this broke datetime
support, so the postgres backend has gained the relevant operation
methods to send dates/times/datetimes directly to the db backend instead
of casting them to strings. Similarly, a new database feature has been
added allowing the uuid to be passed directly to the backend, as we do
with timedeltas.

On the other side, psycopg2 expects an Inet() instance for IP address
fields, so we add a value_to_db_ipaddress method to wrap the strings on
postgres. We also have to manually add a database adapter to psycopg2,
as we do not wish to use the built in adapter which would turn
everything into Inet() instances.

Thanks to smclenithan for the report.

This broke the website design in the sidebar because the line could not be wrapped.

This allows using get_field() early in the app loading process.

Thanks to PirosB3 and Tim Graham.

This finsishes the work started on #16803.
Thanks Simon Charette, Tim Graham and Collin Anderson for the
reviews.

Refs #15101. Patch slightly reworked by Claude Paroz.

Thanks Josh Smeaton and Tim Graham for the reviews.

Thanks Josh Smeaton for the review. Refs #24152.

Thanks Simon and Markus for reviews.

Thanks Tim Graham for the report

refs #24031

Thanks to Tim Graham and Michał Modzelewski for the review.

Fixed #24075 -- Prevented running post_migrate signals when unapplying initial migrations of contenttypes and auth

Thanks Florian Apolloner for the report and Claude Paroz and Tim Graham for the review and help on the patch.

Thanks Tim Graham for the review.