[AHs] Support registering assets on Asset Hubs over bridge

[acatangiu]

Changes

Allows one Asset Hub on one side, to register assets on the other Asset Hub over the bridge.

Rococo <> Ethereum test bridge will be dropped in favor of Westend <> Ethereum test bridge. This PR also changes emulated tests to simulate double bridging from Ethereum<>Westend<>Rococo.

Tests

• e2e test: Westend Asset Hub can register Westend and Ethereum assets on Asset Hub Rococo
• e2e test: Rococo Asset Hub can register Rococo assets on Asset Hub Westend
• e2e test (existing): Users on Ethereum can register Ethereum assets on Asset Hub Westend
• e2e test: transfer Rococo assets from Rococo to Westend and back
• e2e test: transfer Westend assets from Westend to Rococo and back
• e2e test: transfer Ethereum assets (bridged in through Snowbridge) from Westend to Rococo and back

[franciscoaguirre]

🚀

[bkontur]

maybe xcm::TryAs would also work here:

Suggested change

	L: TryInto<Location> + Clone,
	L: TryAs<Location>,

so we don't need to clone anything here:

		let Ok(asset) = asset.try_as() else {
			return false;
		};
		let Ok(origin) = origin.try_as() else {
			return false;
		};

[acatangiu]

the trait TryAs<cumulus_primitives_core::Location> is not implemented for cumulus_primitives_core::Location, which is required by `RemoteAssetFromLocation<AssetsAllowedNetworks, OriginLocation>: ContainsPair<cumulus_primitives_core::Location, cumulus_primitives_core::Location>

although it should work...