top_k: map template arguments
top_k: map template arguments

Added Hash and KeyEqual template arguments to enable unordered_map in top_k implementation.

Signed-off-by: Rafi Einstein <8e7ed78e46f6c81cf24404dc7f3f73947f6f9a79@scylladb.com>

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