Adds columns to track package and test name to test_databases table, and populates them as databases are created using the Broker.
In order to seamlessly work with existing `coder_database` databases with the old schema, the SQL that creates the table and columns is additive and idempotent, so we run it every time we initialize the Broker (once per test binary execution).
We include a transaction level advisorly lock to prevent deadlocks before attempting to alter the schema. I was seeing deadlocks without this.
relates to https://github.com/coder/internal/issues/927
Refactors dbtestutil to use a `Broker` struct to create test databases. Additionally uses a `coder_testing` database to record test databases that are created and when they are dropped.
This is in preparation for the PR above this in the stack which adds a "cleaner" subprocess that cleans out any databases that were left when the test process ends.
Spike Curtis