Related to #10576
This PR introduces quartz to coderd/database/dbpurge and updates the following unit tests to make use of Quartz's functionality:
- TestPurge
- TestDeleteOldWorkspaceAgentLogs
Additionally, updates DeleteOldWorkspaceAgentLogs to replace the hard-coded interval with a parameter passed into the query. This aids in testing and brings us a step towards allowing operators to configure the cutoff interval for workspace agent logs.