indexer: bulk state change processor

[marcelosalloum]

What

Implement a bulk state change processor, so we can easily add extra/custom state change processors for specific contracts.

Why

So we can expand contracts indexing

Issue that this PR addresses

[TODO: Attach the link to the GitHub issue or task. Include the priority of the task here in addition to the link.]

Checklist

PR Structure

• It is not possible to break this PR down into smaller PRs.
• This PR does not mix refactoring changes with feature changes.
• This PR's title starts with name of package that is most changed in the PR, or all if the changes are broad or impact many packages.

Thoroughness

• This PR adds tests for the new functionality or fixes.
• All updated queries have been tested (refer to this check if the data set returned by the updated query is expected to be same as the original one).

Release

• This is not a breaking change.
• This is ready to be tested in development.
• The new functionality is gated with a feature flag if this is not ready for production.