[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`.