Have JDBCFeatureStore declare the FEATURE_DETACHED hint

The renderer relies on the FEATURE_DETACHED hint to determine wheter it's safe to modify in place the geometries instead of cloning them (a caching wrapper would not expose such hint for example), but JDBCFeatureStore does not expose it.
Adding it requires some minor changes in ContentDataStore too since that hint is not a Hints.ClassKey, but just a Hints.Key