Draft: Use `initializer` to configure all database connections

What does this MR do and why?

Currently we selectively re-configure database connections to ensure that proper pool sizes or prepared statements are in place.

This was order dependent, and required a numerous re-establish connections. This moves the configuration aspect early after Rails initializes database ensuring that all required settings are holistically applied to all configs.

This is PoC how this can look and this makes it open for feedback.

Related to: #333411 (closed).

MR acceptance checklist

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