Allow custom predicate to steal BG jobs

What does this MR do?

Issue #218428 (closed) implements a generic BackgroundMigration that is used to copy data between a table and its partitioned copy. Typically when a BackgroundMigration is released, the following release includes a cleanup migration that synchronously processes remaining background jobs, and cleans up remaining data. The migration cleanup logic for partitioning migrations is implemented generically in !35201 (merged).

The BackgroundMigration.steal method is used to synchronously process remaining jobs in a cleanup migration. However, this method selects jobs to process based on the class name. Since the job class implemented for partitioning is generic, selecting jobs based on class name is not granular enough.

This MR implements a change that allows the steal method to accept a block, which is called with the arguments for the job. The steal method processes any job for which the block returns true.

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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