[VDG] Change PrivacyWarnings to IAsyncEnumerable

[ichthus1604]

• Fixes [VDG] Change avoidance calculation blocks all the transaction warnings #11031
• Marked as draft because there is a hard to debug race deadlock that I haven't been able to fix yet, which stops the change avoidance suggestions from yielding, thus the flyout stays busy forever.

[ichthus1604]

@soosr I figured out the problem was due to the early disposal of the CancellationTokenSources.

Marked as ready for review.

[soosr]

nit, but more like a question... Can we somehow prioritize the items here? Because by the testing it seems to me during processing if the first item is a ChangeAvoidance item (and it takes seconds to finish), every other suggestion is waiting to be shown, despite their computation being already done.

We know that always the computation of the ChangeAvoidance items will take the most so put them at the end of the processing?

[ichthus1604]

@soosr Can you share the steps to reproduce this? Adding a 5 second delay in VerifyChangeAsync() line 218, I get all the other suggestions properly shown in the flyout and then the change-related ones appear in the end.

The IAsyncEnumerables are added to a regular List which is then iterated over, so we should get the results in the same order we insert them:

result
	.Combine(VerifyLabels(info, transactionResult))
	.Combine(VerifyPrivacyLevel(info, transactionResult))
	.Combine(VerifyConsolidation(transactionResult))
	.Combine(VerifyUnconfirmedInputs(transactionResult))
	.Combine(VerifyCoinjoiningInputs(transactionResult))
	.Combine(VerifyChangeAsync(info, transactionResult, _linkedCancellationTokenSource));

Unless I'm missing something?

[soosr]

I added a 5 seconds delay before this line

WalletWasabi/WalletWasabi.Fluent/Models/Transactions/PrivacySuggestionsModel.cs

Line 320 in aac6f76

transaction = _wallet.BuildChangelessTransaction(

Just to simulate if the BnB algorithm runs longer (it can run up to 15 seconds).
After this, I did my testing by repeatedly creating a transaction where I know only the Label Management and a Less and a More change avoidance suggestion is possible.

I noticed that sometimes the Label Management option appears later. Taking a look at the logs I could see that when this scenario happened it always appeared after a change avoidance calculation was done.

[soosr]

tACK

[soosr]

Merging since #11163 (comment) is not a blocker. @ichthus1604 think about it, you might have a good idea.