[1.7.x] Added new supported languages
[1.7.x] Fixed #23344 -- Removed duplicate docs for file upload settings.

Backport of c7fa27d702 from master
[1.7.x] Fixed #23352 -- Added tests for MigrationGraph.{forwards,backwards}_plan

Backport of be4baaefe2 from master
[1.7.x] Fixed #23341 -- Better stacktrace error for makemigrations

Backports of 474e1c7 from master