Fixed #23409 -- Extract PasswordResetForm.get_users method.

Allows easier customization of policies regarding which users are allowed to
reset their password.

Thanks Aymeric for review.
Fixed #18757, #14462, #21565 -- Reworked database-python type conversions

Complete rework of translating data values from database

Deprecation of SubfieldBase, removal of resolve_columns and
convert_values in favour of a more general converter based approach and
public API Field.from_db_value(). Now works seamlessly with aggregation,
.values() and raw queries.

Thanks to akaariai in particular for extensive advice and inspiration,
also to shaib, manfre and timograham for their reviews.
Fixed documentation links to Query Expression API.
Fixed typo in 1.8 release notes.
Fixed typo in docs/ref/checks.txt.
Fixed imports in `Sitemap for static views` example
Corrected deprecation warning silencing of SubfieldBase.
Limited lines to 119 characters in django/

refs #23395.
Added missing periods in docs/ref/checks.txt.
Revert "Fixed #23384 -- Allowed overriding part of a dictionary-type setting"

This reverts commit 66757fee7e921ad4c35e0b3f80c25e026100b31c.
Discussions have led to think that this functionality does not
bring significant benefits to justify the added complexity.
Read also discussions on ticket #22734.
Fixed typo in docs/topics/checks.txt.
Fixed #22534: Reinforce swappable documentation
Removed an admonition in the tutorial about the old project layout.

There are no supported versions that use the old layout (<=1.3).
Fixed #22411: Throw a more helpful error if contenttypes doesn't exist.
Fixed #23414 -- Updated version numbers in release process doc.

Thanks jaap3 for the report.
Update docs to be more clear about nested classes (refs #23418)
 switch out recursive dfs for stack based approach, to avoid possibly hitting the recursion limit
Merge pull request #3171 from ClipCard/master

Prevent possible recursion limit issue in migration planning
Fix Python 3 incompatability
Fixed #23427 -- Documented migrate is required before runserver for default projects.