Adds d6 and d7 migrations for audience, membership and roles
Commits from GitHub:
- Alter the default membership type bundle name in field migration rows
- Fix some typos in migration plugins and improved migration module info
- Use the source plugin id instead of the migration id in hook_migrate_prepare_row
- Replace two migration ids with their corresponding source plugin ids in og_migrate_migrate_prepare_row
- Fixed comments in hook_migrate_prepare_row
- Fix the OgFieldD7MigrateTest kernel test
- Add dependencies in the OgFieldD7MigrateTest kernel test
- Skip migrating the og_membership_request field on the default group membership type
- Fix a typo in og_migrate_migrate_prepare_row
- Fix and improve handling default membership type in og_migrate_migrate_prepare_row
- Fix a couple of coding standard issues and add assetions for the form and view displays of the default membership type
Closes #3468826