[stable2506] Backport #9250 (#9359)

Backport #9250 into `stable2506` from acatangiu.

See the
[documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md)
on how to use this bot.

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---------

Co-authored-by: Adrian Catangiu <[email protected]>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: 3 people

polkadot/xcm/xcm-builder/src/universal_exports.rs

@@ -331,6 +331,18 @@ impl<Bridges: ExporterFor, Router: SendXcm, UniversalLocation: Get<InteriorLocat
 	}
 }
 
+impl<Bridges, Router, UniversalLocation> InspectMessageQueues
+	for UnpaidRemoteExporter<Bridges, Router, UniversalLocation>
+{
+	fn clear_messages() {}
+
+	/// This router needs to implement `InspectMessageQueues` but doesn't have to
+	/// return any messages, since it just reuses the `XcmpQueue` router.
+	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
+		Vec::new()
+	}
+}
+
 /// Implementation of `SendXcm` which wraps the message inside an `ExportMessage` instruction
 /// and sends it to a destination known to be able to handle it.
 ///

prdoc/pr_9250.prdoc

@@ -0,0 +1,7 @@
+title: implement InspectMessageQueues for UnpaidRemoteExporter
+doc:
+- audience: Runtime Dev
+  description: Add missing implementation of `InspectMessageQueues` for `UnpaidRemoteExporter`
+crates:
+- name: staging-xcm-builder
+  bump: minor