Implement the utxo-only filtering also for the addresses endpoint

[RCasatta]

This will be needed to implement

    async fn get_address_utxo(
        &self,
        address: &elements::Address,
    ) -> Result<Option<(elements::OutPoint, elements::TxOut)>, Error>;

on a waterfalls client

[valerio-vaccaro]

utack b8818e1

[LeoComandini]

utACK b8818e1, code review