Improve confirmation screen error handling

**What problem are you trying to solve?**
We don't currently have a great way of dealing with unrecoverable errors that occur on a confirmation screen. Currently if an expected error occurs, the confirmation screen might either display no indication something went wrong, or it might close, or it might show the top-level error page (if the error occurred during the render).

**Describe the solution you'd like**
We should catch any unrecoverable errors, log them to Sentry if appropriate, then show the user a message explaining that something went wrong. We should also make clear whether or not the thing they were confirming has been rejected or not.

**Additional context**
I stumbled on this problem while reviewing #7831 , but the problem definitely exists on the signature request UI as well, and probably others too.

Start by reviewing the confirmation-screen work in #7831 and tracing the confirmation and signature request UIs mentioned here. Done means unrecoverable errors are handled consistently, logged to Sentry when appropriate, and the user is told whether the requested action was rejected.

Written by the indexing model from the issue text.