partition_version: Refactor make_partition_snapshot_reader() overloads
partition_version: Refactor make_partition_snapshot_reader() overloads

So that streamed_mutation is created in only one of the overloads and
others delegate to that one. Later there will be common logic added to
the construction and doing this will help avoid a duplication.

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