Fixed typo in error message in django.contrib.sitemaps.
Fixed #22293 -- Avoided renaming many-to-many tables to themselves.

Fixed this for both implementations of _alter_many_to_many, instead of
in `alter_db_table` itself (more implementations).
Fixed #22257 -- Added file output option to dumpdata command.
Merge pull request #2465 from coder9042/ticket_22258

Fixed #22257 -- Added file output option to dumpdata command.
Fixed #22300 -- Fixed crash in migrations when changing non-relational field to relational.
Fixed #22087 -- Made AdminReadonlyField respect ModelForm Meta overrides.
flake8 and doc fixes for refs #22257.
Fixed #22315 -- str/bytes mismatch in staticfiles

Previously, `ManifestFilesMixin.read_manifest` failed in Python 3
because `json.loads` accepts `str` not `bytes`.
Fixed #22331 -- Fixed migrations ProjectState to ignore unmanaged models.
Fixed #12030 -- Validate integer field range at the model level.

Thanks to @timgraham for the review.