row: Prepare row::equal for switch
row: Prepare row::equal for switch

Same as the previous patch, re-implement the row::equal to use
the radix_tree iterator for comparison of two index:cell sequences.

The std::equal() doesn't work here, since the predicate-fn needs
to look at both iterators to call it.key() on (radix tree API
feature), while std::equal provides only the T&s in it.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

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