This patch changes the implementation of atomic_cell and
atomic_cell_or_collection to use the data::cell implementation which is
based on the new in-memory representation infrastructure.
As a prepratation for the switch to the new cell representation this
patch changes the type returned by atomic_cell_view::value() to one that
requires explicit linearisation of the cell value. Even though the value
is still implicitly linearised (and only when managed by the LSA) the
new interface is the same as the target one so that no more changes to
its users will be needed.
The switch to the new in-memory representation will require a larger
parts of the logic be aware of the type of the values they are dealing
with. In most cases it is not a significant burden for the users.
Replace the atomic_cell_or_collection::feed_hash() member function
with the specialization of appending_hash, and use that instead.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
