sstables: file_writer: Generalize bytes& writer to accept bytes_view
sstables: file_writer: Generalize bytes& writer to accept bytes_view

Note that bytes is imlpicitly convertible to bytes_view.

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