RBF for transactions broadcast from another wallet

[darosior]

At the moment the RBF mechanism introduced in #816 only supports referring to one of our PSBTs. It's possible a transaction involving our wallet was broadcast without us having the PSBT (think: threshold multisig), and we might want to RBF this transaction. Because it seems to be a pretty niche usecase, and because it wasn't clear what additional checks we'd need in this case, the first implementation did not support this.

However with the way it ended up being implemented i think it would not be too hard to support creating a RBF for transactions for which we don't have the PSBT: simply query the wallet transaction instead. @jp1ac4 anything i'm missing or otherwise to add here?

[jp1ac4]

I think that's right, we just need the transaction input and output, and so only a small change should be required here.

[pythcoiner]

one related issue happen to an user today: he remove its wallet while an tx was not confirmed, after reimprting it (tx still not confirmed), he cannot RBF beacuse the PSBT don't exists anymore