querier: consume_page(): resolve FIXME related to non-movable consumer
querier: consume_page(): resolve FIXME related to non-movable consumer

Now that #3158 is fixed, we can move the consumer to its place after
the `compaction_mutation_state::start_new_page()` call. No need to keep
it as `std::unique_ptr<>`.

Signed-off-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <20200310185147.207665-1-a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>

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