cql3: make index+primary key restrictions filtering-independent
cql3: make index+primary key restrictions filtering-independent

If full partition key (or full primary key) is used in an indexed
query, it should not require filtering, because queries like that
can be efficiently narrowed down with stricter index restrictions.

avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla