[Meta] Multilingual Bean migrations

Problem/Motivation

Drupal 7 Bean has a quite reliable multilingual support. With the Entity Translation and with the Title module, content authors are able to create Bean content entities with a specified language, and/or translate these entities, including a great revision support.

Bean Migrate has to support the migration from these kind of sources as well.

Proposed resolution

Modify the existing / create new Bean migrations to support the migration of multilingual and translated Bean entities and Bean block placements.

Remaining tasks

• ✅ Done: #3194884: Update the (test) database fixture with bean entity and bean block translations
• ✅ Done: #3195077: Migrate content language settings of Bean types
• ✅ Done: #3194175: Migrate Bean content entity translations
• ✅ Done: #3194177: Migrate Bean block placement translations

API changes

No API changes.
New and (possibly non-BC) modified migrations plugin definitions. (Are these the part of the data model at all?..)

Data model changes

Fully and properly migrated Bean content entities and Bean block placements.