[alias-server] Verify database is appropriately populated in unit tests

Summary:
T3060

These unit tests were created before the app had database functionality and were not modified when database functionality was added.

Add database verifications to existing unit tests. Use a custom server state for unit tests to avoid storing 100 megabytes of chronik tx history.

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14203