NetworkBridge: validator (authorities) discovery api (#1699)

* stupid, but it compiles

* redo

* cleanup

* add ValidatorDiscovery to msgs

* sketch network bridge code

* ConnectToAuthorities instead of validators

* more stuff

* cleanup

* more stuff

* complete ConnectToAuthoritiesState

* Update node/network/bridge/src/lib.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Collator protocol subsystem (#1659)

* WIP

* The initial implementation of the collator side.

* Improve comments

* Multiple collation requests

* Add more tests and comments to validator side

* Add comments, remove dead code

* Apply suggestions from code review

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Fix build after suggested changes

* Also connect to the next validator group

* Remove a Future impl and move TimeoutExt to util

* Minor nits

* Fix build

* Change FetchCollations back to FetchCollation

* Try this

* Final fixes

* Fix build

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* handle multiple in-flight connection requests

* handle cancelled requests

* Update node/core/runtime-api/src/lib.rs

Co-authored-by: Bernhard Schuster <bernhard@ahoi.io>

* redo it again

* more stuff

* redo it again

* update comments

* workaround Future is not Send

* fix trailing spaces

* clarify comments

* bridge: fix compilation in tests

* update more comments

* small fixes

* port collator protocol to new validator discovery api

* collator tests compile

* collator tests pass

* do not revoke a request when the stream receiver is closed

* make revoking opt-in

* fix is_fulfilled

* handle request revokation in collator

* tests

* wait for validator connections asyncronously

* fix compilation

* relabel my todos

* apply Fedor's patch

* resolve reconnection TODO

* resolve revoking TODO

* resolve channel capacity TODO

* resolve peer cloning TODO

* resolve peer disconnected TODO

* resolve PeerSet TODO

* wip tests

* more tests

* resolve Arc TODO

* rename pending to non_revoked

* one more test

* extract utility function into util crate

* fix compilation in tests

* Apply suggestions from code review

Co-authored-by: Fedor Sakharov <fedor.sakharov@gmail.com>

* revert pin_project removal

* fix while let loop

* Revert "revert pin_project removal"

This reverts commit ae7f529d8de982ef66c3007dd1ff74c6ddce80d2.

* fix compilation

* Update node/subsystem/src/messages.rs

* docs on pub items

* guide updates

* remove a TODO

* small guide update

* fix a typo

* link to the issue

* validator discovery: on_request docs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
Co-authored-by: Fedor Sakharov <fedor.sakharov@gmail.com>
Co-authored-by: Bernhard Schuster <bernhard@ahoi.io>

polkadot/node/core/runtime-api/src/lib.rs

@@ -120,6 +120,7 @@ fn make_runtime_api_request<Client>(
 		Request::CandidatePendingAvailability(para, sender) =>
 			query!(candidate_pending_availability(para), sender),
 		Request::CandidateEvents(sender) => query!(candidate_events(), sender),
+		Request::ValidatorDiscovery(ids, sender) => query!(validator_discovery(ids), sender),
 	}
 }
 
@@ -169,7 +170,7 @@ mod tests {
 	use polkadot_primitives::v1::{
 		ValidatorId, ValidatorIndex, GroupRotationInfo, CoreState, PersistedValidationData,
 		Id as ParaId, OccupiedCoreAssumption, ValidationData, SessionIndex, ValidationCode,
-		CommittedCandidateReceipt, CandidateEvent,
+		CommittedCandidateReceipt, CandidateEvent, AuthorityDiscoveryId,
 	};
 	use polkadot_node_subsystem_test_helpers as test_helpers;
 	use sp_core::testing::TaskExecutor;
@@ -258,6 +259,10 @@ mod tests {
 			fn candidate_events(&self) -> Vec<CandidateEvent> {
 				self.candidate_events.clone()
 			}
+
+			fn validator_discovery(ids: Vec<ValidatorId>) -> Vec<Option<AuthorityDiscoveryId>> {
+				vec![None; ids.len()]
+			}
 		}
 	}