Description
In order to make MW history reduced snapshot updates automatically, we need to:

• Create an airflow job that updates the snapshot value in Cassandra's aqs.config table when the new data is ready. Done as part of T352948.
• Modify aqsassist to include a DynamicConfig object that is able to read config properties (the snapshot) from Cassandra's aqs.config table.
• Modify aqsassist to factor out Druid and Cassandra configuration, since now some services will need to access both of them.
• Add the aqs.config table to Cassandra's test environment, so integration tests can use the new code.