Add candidate info to OccupiedCore (#2134)

* guide: add candidate information to OccupiedCore

* add descriptor and hash to occupied core type

* guide: add candidate hash to inclusion

* runtime: return candidate info in core state

* bitfield signing: stop querying runtime as much

* minimize going to runtime in availability distribution

* fix availability distribution tests

* guide: remove para ID from Occupied core

* get all crates compiling

polkadot/roadmap/implementers-guide/src/runtime/inclusion.md

@@ -14,6 +14,7 @@ struct AvailabilityBitfield {
 
 struct CandidatePendingAvailability {
   core: CoreIndex, // availability core
+  hash: CandidateHash,
   descriptor: CandidateDescriptor,
   availability_votes: Bitfield, // one bit per validator.
   relay_parent_number: BlockNumber, // number of the relay-parent.