XCM: Tools for uniquely referencing messages (#7234)

* Tools for unique topic references

* Formatting

* Naming

* Repot into routing.rs.

* More things done

* Universal Exporter supports topic-as-reference

* Some tests for the topic routing

* More tests

* Paid bridge tests

* Add message ID to sending events

* Formatting

* fix and integrate into test nets

* Move DenyThenTry and friend from Cumulus

* Append SetTopic rather than prepend

* Docs

* Docs

* Work with new ProcessMessage ID API

* Formatting

* Fix build

* Fixes

* Formatting

* Update xcm/xcm-builder/src/barriers.rs

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>

* Update xcm/xcm-builder/src/routing.rs

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>

* Docs

* Rename message_hash

* Formatting

* ".git/.scripts/commands/fmt/fmt.sh"

* Rename

* Another Rename

* ".git/.scripts/commands/fmt/fmt.sh"

* ".git/.scripts/commands/fmt/fmt.sh"

* Update xcm/xcm-builder/src/routing.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

polkadot/xcm/pallet-xcm-benchmarks/src/generic/benchmarking.rs

@@ -209,7 +209,7 @@ benchmarks! {
 			assets.clone().into(),
 			&XcmContext {
 				origin: Some(origin.clone()),
-				message_hash: [0; 32],
+				message_id: [0; 32],
 				topic: None,
 			},
 		);
@@ -266,7 +266,7 @@ benchmarks! {
 			max_response_weight,
 			&XcmContext {
 				origin: Some(origin.clone()),
-				message_hash: [0; 32],
+				message_id: [0; 32],
 				topic: None,
 			},
 		).map_err(|_| "Could not start subscription")?;