[TEST] prevent dummy documents from being indexed in testSimpleQueryString() since scores are compared
Fix FieldDataWeighter generics to accept RamUsage instead of AtomicFieldData

The `FieldDataWeighter` allowed to use a concrete subclass of the caches
generic type to be used that causes ClassCastException and also trips the
CirciutBreaker to not be decremented appropriately.

This was tripped by settings randomization also part of this commit.

Closes #6260