sstables: treat sstables in upload dir as needing view build
sstables: treat sstables in upload dir as needing view build

In some cases, sstables put in the upload dir should have view updates
generated from them. In order to avoid moving them across directories
(which then involves handling failure paths), upload dir will also be
treated as a valid directory where staging sstables reside.
Regular sstables that are not needed for view updates will be
immediately moved from upload/ dir as before.

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