test: add unit tests for query plan exclusion, LRU cache, and LWT determinism

Add tests for make_query_plan_with_exclusion in RoundRobin, DCAware, and
RackAware policies. Add cache tests (hit, miss, eviction, topology
invalidation, disabled) and LWT determinism tests for TokenAwarePolicy.
Update existing tests to set up token_map mocks and shuffle_replicas=False
to match the new TokenAwarePolicy implementation.

Author: mykaul