Currently, each frozen mutation we get from
system_keyspace::query_mutations is unfrozen in whole
to a mutation and only then we check its key with
the provided `accept_keyspace` function.
This is wasteful, since they key can be processed
directly form the frozen mutation, before taking
the toll of unfreezing it.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
(cherry picked from commit 52234214e5)
b7de15dc60