added an ID index and delete old view rows

[bashir2]

Description of what I changed

Adds an index on the id columns (and makes that column mandatory) and deletes record with the same resource IDs before adding them to the DB. This is required for #916 to be able to update old view rows.

E2E test

TESTED:

Ran the pipeline for both small and large datasets (~16M observations). The impact of the index/deletion on performance seems to be ~3% or less (depending on various scenarios tested).

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[chandrashekar-s]

Thanks for the changes @bashir2, there are few only few comments which are not that critical. I am approving the changes.

[bashir2]

Thanks @chandrashekar-s for the review; I marked some of your comments to address in a follow-up PR [soon].