zcash_client_sqlite: Add a "golden test" framework

[str4d]

It would be beneficial to be able to generate SQLite database states that we can then test, for example that exhibit a bug that a particular migration is intended to fix (and that we want to ensure is a) fixed, and b) does not revert). However, we also want to avoid enabling the xz vulnerability by committing arbitrary binary data to the repository.

We should add a framework to zcash_client_sqlite (or to the devtools crate as necessary) such that when a developer adds a migration, they can also:

• Write a script that uses a specific public version of zcash_client_sqlite (and associated crates) to deterministically generate a SQLite database.
• Commit both the script and the resulting database.
• Load the database in a test to verify the migration.

CI should detect the commits that create golden test databases, and verify that the committed binary data is reproducible from the script. That way, PR reviewers can just review the generation script, rather than needing to inspect the binary data.