* Apply suggestions from #1364 code review

- use CoreState, not CoreOccupied
- query for availability chunks, not the whole PoV
- create a stub `fn availability_cores`

* link to issue documenting unimplemented

* implement get_availability_cores by adding a new runtime api request

* back out an unrelated change properly part of #1404

* av-store: handle QueryChunkAvailability

* simplify QueryDataAvailability

* remove extraneous whitespace

* compact primitive imports

* Initial commit

* WIP

* Make atomic transactions

* Remove pruning code

* Fix build and add a Nop to bridge

* Fixes from review

* Move config struct around for clarity

* Rename constructor and warn on missing docs

* Fix a test and rename a message

* Fix some more reviews

* Obviously failed to rebase cleanly