[feature]: FundChannel: allow funding with multiple asset types

[ZZiigguurraatt]

FundChannel only allows a single asset_id to be used for funding the channel. FundChannel does put sats in a channel, so we do have multi asset channels then, but we can only attach one taproot asset to the channel. We should be able to attach multiple taproot assets to a channel so that we can reduce the number of channels and on chain activity.