[xcm] Fix SovereignPaidRemoteExporter and DepositAsset handling (#3157)

This PR addresses two issues:
- It modifies `DepositAsset`'s asset filter from `All` to
`AllCounted(1)` to prevent potentially charging excessive weight/fees.
This adjustment avoids situations where fees could be calculated based
on the count of assets, as illustrated
[here](https://github.com/paritytech/polkadot-sdk/blob/master/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/weights/xcm/mod.rs#L38-L46).
- It encapsulates `DepositAsset` with `SetAppendix` to ensure that
`fees` are not trapped in any case. For instance, this prevents issues
when `ExportXcm::validate` encounters an error during the processing of
`ExportMessage`.

cumulus/parachains/runtimes/assets/test-utils/src/test_cases_over_bridge.rs

@@ -244,6 +244,11 @@ pub fn limited_reserve_transfer_assets_for_native_asset_works<
 						_ => Err(ProcessMessageError::BadFormat),
 					})
 					.expect("contains BuyExecution")
+					.match_next_inst(|instr| match instr {
+						SetAppendix(_) => Ok(()),
+						_ => Err(ProcessMessageError::BadFormat),
+					})
+					.expect("contains SetAppendix")
 			} else {
 				xcm_sent
 					.0

cumulus/parachains/runtimes/bridge-hubs/test-utils/src/test_cases/mod.rs

@@ -578,6 +578,10 @@ where
 			fees: Asset { id: AssetId(Location::new(1, [])), fun: Fungible(34333299) },
 			weight_limit: Unlimited,
 		},
+		SetAppendix(Xcm(vec![DepositAsset {
+			assets: Wild(AllCounted(1)),
+			beneficiary: Location::new(1, [Parachain(1000)]),
+		}])),
 		ExportMessage {
 			network: Polkadot,
 			destination: [Parachain(1000)].into(),
@@ -614,7 +618,6 @@ where
 				]),
 			]),
 		},
-		DepositAsset { assets: Wild(All), beneficiary: Location::new(1, [Parachain(1000)]) },
 		SetTopic([
 			36, 224, 250, 165, 82, 195, 67, 110, 160, 170, 140, 87, 217, 62, 201, 164, 42, 98, 219,
 			157, 124, 105, 248, 25, 131, 218, 199, 36, 109, 173, 100, 122,