Adding changes to allow Postgres-to-Postgres migrations with schema, trigger, and index migration support via mirrors

[jpruiz114]

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[CLAassistant]

All committers have signed the CLA.

[jpruiz114]

Some notes to self and for visibility:

I've created this repository with some additional files to run PeerDB locally and a few test PostgreSQL databases for the Postgres-to-Postgres migrations supporting schema, trigger, and index migration:

https://github.com/jpruiz114/peerdb-postgres-improvement-testing

[iskakaushik]

@jpruiz114 -- directionally I like this change, I'll take a deeper look tomorrow. Could you sign the CLA please :)

[jpruiz114]

I am making sure that all the indexes, triggers, and constraints are moved from the source PostgreSQL into the target PostgreSQL via the mirror process. I still see some discrepancies which I'm trying to fix. I rebased all my commits into a single one and my feature branch for this draft against the latest changes of the main branch.

[jpruiz114]

I feel comfortable with the latest changes where I can see all the schema, trigger, and index migration happening as expected.

I will rebase against the latest changes, test again, push, and mark this pull request as ready for review.

Thanks.