Fixed #20401 -- ContentTypeManager.get_for_model reads from db_for_read.

Thanks Simon Charette and Tim Graham for the reviews.
Making SQL management commands migration aware.
Merge pull request #2743 from valberg/migration_aware_sql_commands

Making SQL management commands migration aware.
Fixed #22682 -- `makemigrations` will create `MIGRATION_MODULES` package

`makemigrations` will automatically create the package specified
in `MIGRATION_MODULES` if it doesn't already exist.

Thanks ovidiuc4 for the report.
Fix test failure caused by 3149cdce32e7261b2d44128ab712c4d4f1a5d429
Merge pull request #2744 from mmardini/MIGRATION_MODULES

Fixed #22682 -- `makemigrations` will create `MIGRATION_MODULES` package
Improved deprecation plan links in release notes.
Fix additional test failures caused by migration pollution