xcm-router: Update `message_length_scale_encoded`

[NunoAlexandre]

https://github.com/centrifuge/connectors/blob/baeef4ab8608b1d13218c5269363a1f50f7db3c6/src/routers/xcm/Router.sol#L159-L183

Changes

• The message_length_scale_encoded function now only supports the v1 flow with TransferTrancheTokens but for v2 it needs to support all the v2 outgoing messages

[NunoAlexandre]

This has been done by @mustermeiszer a couple of weeks ago before the release 🧹

[hieronx]

Looks like it was only partially completed https://github.com/centrifuge/liquidity-pools/blob/42452959ee11ab6a8f64b096efa471dbdcb3fbb8/src/gateway/routers/xcm/Router.sol#L156