MonadBlockChain instance for Contract does not take TxOpts into account

[florentc]

The MonadBlockChain instance for Plutus Contract does not take options TxOpts in transaction skeletons into account. Especially regarding balancing and ensuring every utxo has the minimum required amount of ada.

For example, take a skeleton that specifies a public key utxo should be spent to mint an NFT and put in at a script address, with the adjustUnbalTx option enabled. The instance for Contract generates a transaction with only one script output carrying only the NFT. Unlike the transaction generated by Direct, it misses a payback output for the public key and the 2 adas in the script output.

[VictorCMiraldo]

This is definitely related to #78, which contains suggestions on fixing this

[mmontin]

Closing this because this will be handled only when / if we decide to have an instance for the contract monad.