feat: extract sbtc contract calls block observer

[djordon]

Description

• Closes [Feature]: Block observer - extract withdraw requests #205
• Closes [Feature]: Block observer - extract withdraw accept transactions #206
• Closes [Feature]: Block observer - extract withdraw reject transactions #207
• Closes [Feature]: Block observer - extract deposit accept transactions #208
• Closes [Feature]: Block observer - extract set aggregate key transactions #210
• Closes [Feature]: Block observer writing stacks block #212

This might also address #209, but I'm not sure.

Changes

1. Modify one of the functions in the DbWrite trait to use the model types as input. This keeps the interface a bit more logical and makes it easier to test.
2. Rewrote the functions that wrote stacks blocks to send slices of the correct type, instead of sending JSON. This allows us to make use of the actual type that we want to write.
3. Finish implementation of the function that writes stacks blocks in the block observer.

Testing information

This PR is mostly a refactor. The core functionality was added in 2e30ef3, but subsequent commits addressed some oddities in the previous code.

[netrome]

This is great stuff so far. What we should also do (either here or as follow-ups) is to populate some dedicated tables for the different transaction types. We should:

• Parse any calls to rotate-keys-wrapper and write the updated signer set into a table. Right now the storage model has the aggregate_key_transactions table that tracks the aggregate keys. I think we could rename this to key_rotations, and we also need to track the updated signer set, so we need to add a field for that as well.
• Populate the deposit_responses and withdraw_responses tables in the state model.

[AshtonStephens]

LGTM, though how are we ultimately getting the data from the deleted functions? For example with the function below:

    fn extract_update_signer_set_transactions(&self, _transactions: &[stacks::StacksTransaction]) {
        // TODO(#208): Implement
    }

Do we no longer need that data?

[djordon]

LGTM, though how are we ultimately getting the data from the deleted functions? For example with the function below:

    fn extract_update_signer_set_transactions(&self, _transactions: &[stacks::StacksTransaction]) {
        // TODO(#208): Implement
    }

Do we no longer need that data?

We do, it's just done in the BlockObserver::write_stacks_blocks function. That function extracts the relevant transactions and writes them all to the database as two queries.