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>

pallets/xcm/src/lib.rs

@@ -0,0 +1,92 @@
+// Copyright 2020-2021 Parity Technologies (UK) Ltd.
+// This file is part of Cumulus.
+
+// Cumulus is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Cumulus is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Pallet for stuff specific to parachains' usage of XCM. Right now that's just the origin
+//! used by parachains when receiving `Transact` messages from other parachains or the Relay chain
+//! which must be natively represented.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use cumulus_primitives_core::ParaId;
+use codec::{Encode, Decode};
+use sp_runtime::traits::BadOrigin;
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	#[pallet::pallet]
+	#[pallet::generate_store(pub(super) trait Store)]
+	pub struct Pallet<T>(_);
+
+	/// The module configuration trait.
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::error]
+	pub enum Error<T> {}
+
+	#[pallet::hooks]
+	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {}
+}
+
+/// Origin for the parachains module.
+#[derive(PartialEq, Eq, Clone, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
+pub enum Origin {
+	/// It comes from the (parent) relay chain.
+	Relay,
+	/// It comes from a (sibling) parachain.
+	SiblingParachain(ParaId),
+}
+
+impl From<ParaId> for Origin {
+	fn from(id: ParaId) -> Origin {
+		Origin::SiblingParachain(id)
+	}
+}
+impl From<u32> for Origin {
+	fn from(id: u32) -> Origin {
+		Origin::SiblingParachain(id.into())
+	}
+}
+
+/// Ensure that the origin `o` represents a sibling parachain.
+/// Returns `Ok` with the parachain ID of the sibling or an `Err` otherwise.
+pub fn ensure_sibling_para<OuterOrigin>(o: OuterOrigin) -> Result<ParaId, BadOrigin>
+	where OuterOrigin: Into<Result<Origin, OuterOrigin>>
+{
+	match o.into() {
+		Ok(Origin::SiblingParachain(id)) => Ok(id),
+		_ => Err(BadOrigin),
+	}
+}
+
+/// Ensure that the origin `o` represents is the relay chain.
+/// Returns `Ok` if it does or an `Err` otherwise.
+pub fn ensure_relay<OuterOrigin>(o: OuterOrigin) -> Result<(), BadOrigin>
+	where OuterOrigin: Into<Result<Origin, OuterOrigin>>
+{
+	match o.into() {
+		Ok(Origin::Relay) => Ok(()),
+		_ => Err(BadOrigin),
+	}
+}