Add RPC response snapshot tests

[teor2345]

Motivation

In the address index review meeting last week, we talked about testing address indexes.

One of the ways we can test is by checking that Zebra's RPC responses match a snapshot of a previous response. If the changes are intentional, we can update the snapshot. If they aren't, we can fix the PR.

These snapshots also help us make sure that differences between Zebra and zcashd stay fixed (#4130).

Designs

We can test RPCs by:

• adding some blocks to a Zebra state
• sending an RPC query
• snapshotting the response using cargo insta

We already have similar tests for the Zebra state database.

Related Work

• Script that shows the differences between Zebra and zcashd RPC responses #4130