utils: managed_bytes: introduce with_linearized()
utils: managed_bytes: introduce with_linearized()

This is a temporary scaffold for weaning ourselves off
linearization. It differs from with_linearized_managed_bytes in
that it does not rely on the environment (linearization_context)
and so is easier to remove.

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