Refactor: the user interface should be a cancelable promise

[aaroncox]

Right now the only cancelable promise we have is the prompt elements, which means that if the modal is closed, only the prompt elements be canceled.

This kind of illustrates the problem.

• I trigger a signing request
• Instead of completing the request, I close the modal in the web-ui-renderer.
• The promise waiting for it doesn’t cancel, it still is processing, which is why when you see me close the WAX window, all the sudden the error pops up.

The entire web ui renderer would have to be refactored into a cancelable promise to resolve this without a prompt. That’s the right solution I think, but is going to be a significant rewrite to pull off, which I don’t want to have to do at this very moment due to the design work going on.

Internal thread: https://greymass.slack.com/archives/C045MUS6F0F/p1678473763146879

[aaroncox]

The workaround right now is to use the prompt element during these "waiting" phases, since that is cancelable. The autocorrect plugin is currently doing this, and the Anchor plugin is doing something similar with a countdown.