XCM revamp & Ping pallet (#391)

* Add spambot

* Fixes

* Add some extra functions to spambot, bump version

* Lock..

* Aggregate HRMP (XCMP/HMP) messages. Payloads for spambot.

* Fix tests, bump Polkadot.

* Fix HMP tests

* Rename Hrmp -> Xcmp for handler/sender

* Use master branch

* Test Xcm message passing & rename away from HMP

* Docs

* Introduce fee payment mechanics into XCM.

* Rename spambot -> ping

* Lock

* XCMP message dispatch system reimagining

- Moved most of the logic into xcm-handler pallet
- Altered the outgoing XCMP API from push to pull
- Changed underlying outgoing queue data structures to avoid multi-page read/writes
- Introduced queuing for incoming messages
- Introduced signal messages as a flow-control sub-stream
- Introduced flow-control with basic threshold back-pressure
- Introduced overall weight limitation on messages executed
- Additonal alterations to XCM APIs for the new system

* Should process any remaining XCM messages when we're not doing anything else.

* Update API usage and preparation for the big build.

* Some build fixes

* Build fixes

* xcm-handler builds

* Fix warnings

* Docs

* Parachains system builds

* Parachain runtime building

* Fix build

* Introduce transfer_asset specialisation.

* Fixes

* Two-stage upgrade for parachains.

* Fixes

* Fixes

* Updates for message sending.

* Repotting/renaming. Add primitives/utility.

* Remove real-overseer and bump refs

* Configure & document Rococo XCM runtime.

* Add shell runtime, some companion changes for #8589

* Bumps & fixes

* Fix test

* Build fix

* Update pallets/xcmp-queue/src/lib.rs

Co-authored-by: Amar Singh <asinghchrony@protonmail.com>

* Make tests compile

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove unused

* remove unused event stuff

* Adds proper validation-worker to make integration tests work

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* import saturating

* remove panic test

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Amar Singh <asinghchrony@protonmail.com>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Bastian Köcher <info@kchr.de>

client/collator/src/lib.rs

@@ -400,10 +400,15 @@ mod tests {
 	use cumulus_test_runtime::{Block, Header};
 	use futures::{channel::mpsc, executor::block_on, StreamExt};
 	use polkadot_node_subsystem_test_helpers::ForwardSubsystem;
-	use polkadot_overseer::{AllSubsystems, Overseer};
+	use polkadot_overseer::{AllSubsystems, Overseer, HeadSupportsParachains};
 	use sp_consensus::BlockOrigin;
 	use sp_core::{testing::TaskExecutor, Pair};
 
+	struct AlwaysSupportsParachains;
+	impl HeadSupportsParachains for AlwaysSupportsParachains {
+		fn head_supports_parachains(&self, _head: &PHash) -> bool { true }
+	}
+
 	#[derive(Clone)]
 	struct DummyParachainConsensus {
 		client: Arc<Client>,
@@ -454,8 +459,13 @@ mod tests {
 
 		let all_subsystems =
 			AllSubsystems::<()>::dummy().replace_collation_generation(ForwardSubsystem(sub_tx));
-		let (overseer, handler) = Overseer::new(Vec::new(), all_subsystems, None, spawner.clone())
-			.expect("Creates overseer");
+		let (overseer, handler) = Overseer::new(
+			Vec::new(),
+			all_subsystems,
+			None,
+			AlwaysSupportsParachains,
+			spawner.clone(),
+		).expect("Creates overseer");
 
 		spawner.spawn("overseer", overseer.run().then(|_| async { () }).boxed());