Return attrs for more media repo APIs. (#16611)

changelog.d/16611.misc

synapse/handlers/profile.py

synapse/handlers/sso.py

synapse/media/media_repository.py

synapse/media/url_previewer.py

synapse/rest/media/thumbnail_resource.py

synapse/storage/databases/main/media_repository.py

tests/media/test_media_storage.py

tests/rest/admin/test_media.py

tests/rest/media/test_media_retention.py