Add DbDataStore using the default H2 db in the default repository.xml resource

By default, resources/src/main/resources/org/hippoecm/repository/repository.xml doesn't define a (optional) DataStore. So, every binary data is stored by PersisteceManager, not by DataStore.
(In production, we always set DbDataStore.)
The default setup without DataStore has been good enough so far in local development.
However, as of CMS-10204, CMS Console may be able to show Jackrabbit Content Identity value if the binary data is from DataStore.
So, it should be better to configure an H2 based DbDataStore like normal production to test CMS-10204 properly even in local simple testing env.