Calling addOperationToQueue to often causes race condition

Problem/Motivation

Calling Queue::addOperationToQueue() too often causes

Duplicate entry 'batch_plugin_queue_worker:<ID>'

Suggested fix: Fix the queue context write to be upsert-style instead of delete-then-insert.

The current queue context logic is vulnerable because it does:

delete row for queue_id
insert row for queue_id

That is not safe when multiple requests run at the same time.

Change it to a merge() so Drupal performs an insert-or-update operation.