Made the vendored NamedTemporaryFile work as a context manager. Refs #22680.

This fixes a regression on Windows introduced by b7de5f5.

Thanks Tim Graham for the report and review.
Prevented markup escape in 'Welcome to Django' page

Fixes a regression introduced in 5f24cf9705. Refs #22635.
Thanks A.J. May for spotting the regression.
Fixed #22813 -- Updated Pillow URL in documentation
Fixed #22811 -- Allowed setting both the old and new TEST database settings.

An ImproperlyConfigured exception will be raised they mismatch.
Silenced deprecation warnings for refs #22811 and fixed build.
Fixed #22818 -- Clarified you need to cd into the Django clone.

Thanks Josh Parris.
Fixed #22814 -- Allowed ISO-8601 [+-]hh timezone format in parse_datetime
Merge pull request #2804 from AsymmetricVentures/issue22814

Fixed #22814 -- Allowed ISO-8601 [+-]hh timezone format in parse_datetime
Fixed a staticfiles test on Windows.
Fixed #22823 (and partly #22563) - FKs from unmigrated apps breaking state.

Thanks to bendavis78 for the test and diagnostic work.
Fix test breakage from previous state fix
Fixed #22349 -- Added a note clarifying `RawQuerySet` has no `__len__`.

Thanks cdestigter for the report.