Backfill new uploads_9ba88c4165 partioned table

What does this MR do and why?

This MR back-fills the new partitioned uploads_9ba88c4165 table that was created with Create partitioned table for uploads (!175203 - merged).

• Update #uploads_sharding_key for models using uploads (now that they are all back-filled).
• Enqueue BackfillPartitionedUploads background migrations and for each batch executes one query per model that will back-fill uploads for which the associated model still exists using it's sharding key values.

Full list of back-fill queries:

• 398199-backfill-uploads-partitions.sql

References

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• #398199

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Related to #398199