Draft: Add Queueable module - BBO

Ref: #561698 (closed)

What does this MR do and why?

This MR adds a new module responsible for enqueueing an operation, here how it looks like:

Gitlab::Database::BackgroundOperation::Worker.queue(job_class_name, table_name, column_name)

It will create a new record to background_operation_workers which will be used to schedule batched jobs of a given operation.