Fixed #22487: Separated schema migration from data migration in test

The data migration failed on Oracle, killing the entire test suite.

Thanks timo for reporting the Oracle breakage,
and andrewgodwin for suggesting the solution.
Added link to data migrations in initial data deprecation note
Added note to alphabetize AUTHORS.
Fixed typo in docs/ref/forms/validation.txt.
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