[VDG] Add confirmation time for coinjoins placeholders

[SuperJMN]

Adds the UI part of confirmation time estimation for coinjoins.

[SuperJMN]

@soosr This is waiting for something similar to what we did for transactions:

TransactionFeeHelper.TryEstimateConfirmationTime(_walletVm.Wallet, transactionSummary.Transaction, out var estimate);

I've added TODO tags to include the actual estimation time calculation when it's available. Please, ping me when the this required implementation is ready :)

[adamPetho]

I'm on implementing the business logic for this and also for receive tx and payjoins etc (for all txs which has foreign input). WIP.

[soosr]

tACK.

Edited the description so I removed the "Fixes" keyword, it's going to be fixed when @adamPetho implements the business part.