Add the possibility to exclude the search_api_attachments table from backup in backup and migrate module

Problem/Motivation

We would like to exclude the search_api_attachments table from our backups as it takes a lot of space and forbids restore of those huge backup files using the Backup and Migrate module.

The search_api_attachments should be available for selection in the Exclude data from these tables in the B&M backup form. It's currently not present in the table selection list.

Don't know how the Backup and Migrate gets this table list from Drupal, may be some kind of configuration somewhere?