11158: Fixes & test updates for ProjectDirectory.

11158: Fixes & test updates for ProjectDirectory.

* list_all() orders by uuid and uses it for paging.

* Move dynamic item lookup from __contains__ to __getitem__ to fix some tests.

* Remove test that check for pipeline objects because ProjectDirectory doesn't
create them any more.

* FuseSharedTest now runs in a multiprocess worker to avoid deadlock.

* Tweak local_store_get used in testing to raise NotFoundError for consistency
with real get().

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <peter.amstutz@curoverse.com>