In-line tracker creation to BulkImportWorker

What does this MR do and why?

In-line tracker creation to BulkImportWorker

This MR is a pre-cursor to extracting the BulkImportWorker code into a separate service, allowing the Worker itself to focus primarily on scheduling/retry concerns.

It implements the in-lining of the pipeline tracker creation as per this code review comment:

!57153 (comment 547953119)

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