Milestones need to track if they have been withdrawn or not

[samelamin]

We currently keep track of the total funds withdrawn, but with the move to multichain we need to keep track of which milestone was approved, then withdrawn

we currently have a bool flag when a milestone is approved, we need the same for withdrawn. We also need a paymentAddress for when users are withdrawing to a different walllet in another chain

withdrawn: bool;
paymentAddress:Vec<u8>;