[TEST] thrown error when there are no REST tests to run
Fix hashCode values of aggregations' BytesValues.

This commit removes FilterBytesValues which is very trappy as the default
implementation forwards all method calls to the delegate. So if you do any
non-trivial modification to the terms or to the order of the terms, you need
to remember to override currentValueHash, copyShared, and this is very
error-prone.

FieldDataSource.WithScript.BytesValues and ScriptBytesValues now return correct
hash codes, future bugs here would be catched by the new assertion in
SortedUniqueBytesValues.

This bug was causing performance issues with scripts as all terms were assumed
to have the same hash code.

Close #5004
Add script support to value_count aggregations.

Close #5001