remove registry imports as it is no longer used
remove registry from setup, no longer used
update ncsvpn backend to new api, and no longer uses registry
remove registry and subscription as they are no longer used (yes.....)
refactor state handling to nsi2 states
more state fixes
implement reserve abort properly in aggregator
fix timeout api and handling in aggregator
fix yielding the right deferreds a couple of places in aggregator and a bit of cleanup
join dud backend test and aggregator test into a single tester to avoid method duplication
fix abort/timeout handling in backend so abort+timeout are not emitted on timeout, only timeout
remove aggregator test as it is now contained in test_providers module
update interface test
update ncsvpn test partially to new api, mainly to remove use registry use so module import does not fail