Fixed #24034 -- Don't always overwrite deconstruct path.

Made deconstruct path overwriting for ArrayField conditional,
so it only occurs when the deconstructed field is an instance
of ArrayField itself and not a subclass.

Correct scoping of savepoint example

It helps if there are the correct number of microseconds in a second.

A field for storing periods of time - modeled in Python by timedelta. It
is stored in the native interval data type on PostgreSQL and as a bigint
of microseconds on other backends.

Also includes significant changes to the internals of time related maths
in expressions, including the removal of DateModifierNode.

Thanks to Tim and Josh in particular for reviews.

Refs #24007. Thanks Tim Graham for his help with the patch.

Refs #24015.

Thanks Tim Graham for the report and initial patch.

Thanks Tim Graham for the review.

This prevents AppRegistryNotReady errors when unpickling Django
models from an external script.

It may not be installed on all systems.

Thanks Brian Jacobel for the report. refs django/djangoproject.com#197

Previously Publisher.objects.filter(book=val) would target
book.object_id if book is a GenericRelation. This is inconsistent to
filtering over reverse foreign key relations, where the target is the
related model's primary key.

Thanks kmmbvnr for the report.

Fixed #23893: Added tzinfo to constant datetime in unit test

Added tzinfo to y2k constant (01/01/2000) in
custom_lookups.tests.DateTimeLookupTests.test_datetime_output_field
to fix warning message regarding naive datetimes.

Copied technique from schema tests.

Thanks to Tim Graham for reporting the issue; refs #23822

A default is no longer required.