mm ui: make CEX/DEX failed trade warnings persistent until dismissed/acknowledged

[artikozel]

The addition of failed CEX/DEX trade warnings in the Bison Wallet market maker is a fantastic one in terms of inventory management. However, currently these warnings appear after the last failed trade without the user quickly realising how many such failed trades have occurred in a given bot run and disappear immediately after a successful trade is made. A better solution would be to make them persistent for all the failed trades, so they user would realise the scale of the inventory imbalance more quickly and make them disappear only after they have been manually acknowledged by the user, because if they disappear autimatically upon a successful trade they fail to inform the user of the event.

[martonp]

Good idea, thanks.