Implement <indexed-entities> config for protobuf payloads in indexed caches

This config element must have the same meaning as for indexed classes.
It must list FQNs of indexed types.

<indexed-entity> occurrence must also be set to 1..n in xsd.

All indexed objects that have a type not included in the list should trigger a warning.

All searches against types not included in the list should trigger a warning.

These 2 warnings will become errors in next major version (12).