Use Drupal 8/9 batch API

Here is a reroll of above patch against 2.x. Also updating the other issues.

Previous patches do not work as this module needs to delete the source terms, and dispatch the event at the end of/ after the batch has finished.

Currently in the MR for https://www.drupal.org/project/term_reference_change/issues/3142776 🐛 Use Batch API to avoid timeouts when updating large number of references Needs work the function batchMigrateReference creates the batch job - i've added a patch for this MR in https://www.drupal.org/project/term_reference_change/issues/3142776#comm... 🐛 Use Batch API to avoid timeouts when updating large number of references Needs work which instead returns the batch operations.

In combination with this patch, the term merge worked using batch API, haven't gone through and updated/run the module tests (doesn't look like anyone has with Drupal 10).

Rerolling patch from #14 for 2.x Beta6

Andriy Khomych → changed the visibility of the branch 3013117-use-drupal-89 to hidden.

Here is a MR ready to be reviewed - https://git.drupalcode.org/project/term_merge/-/merge_requests/24