Create db utils for common operations related to built-in models

[pharr117]

The indexer provides a couple built-in models in use throughout the main indexer loop that may be useful for custom parsers. These include:

1. Address model
2. Denom model

We should add utils to help custom parsers/indexers handle these models. These could include:

1. Find ops
2. FindOrCreate ops

These models have unique indexes on them, so these will provide useful utils while reducing errors.

[pharr117]

This has been pushed along in various PRs, marking this as done.