Prevent BulkImportEntityWorker from being incorrecly deduplicated

What does this MR do and why?

To fix Fix Direct Transfer stages execution order (!132320 - merged), I changed how BulkImports::EntityWorker initiates the execution of stages and changed the worker deduplicate strategy from until_executing to until_executed.

Recently I noticed that some workers were getting incorrectly deduplicated, causing the worker to stop being re-enqueued and causing the migration to get stuck. To fix the problem, we changed the worker to use the option deduplicate :until_executed, if_deduplicated: :reschedule_once !135786 (merged). However, even with reschedule_once, workers occasionally aren't rescheduled causing the migration to get stuck.

For example, on Kibana we can see that not all workers that were deduplicated were rescheduled

To fix the problem, this MR changes the deduplicate strategy back to until_executing and uses lease guard to prevent the same code from being executed twice

Related to: #432813 (closed)

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