Friendlier Error Messages for Jetstream 2

@ssudarsh has observed a few issues with how we're capturing errors and presenting them to the user:

1. Error messages in the messages view don't persist on page refresh, so it's hard to review them later for troubleshooting purposes -- opportunity to persist messages in local storage or ship them somewhere for later analysis
2. Error messages in the messages view are sometimes confusing, and it's difficult to produce examples for this because of 1.
3. Error message toasts (which pop up in the upper right-hand column) sometimes appear several at a time, and they appear to be the same -- opportunity for us to de-duplicate error messages. (created #504 (closed))

Let's meet with Sanjana to confirm/correct our understanding, then get each of these separated out into their own issues.

Also, from @debyly:

I had an error tooltip in the top right for most of the time that I used exosphere because I didn't realize I could interact with it. Perhaps give users a cue that the window is interactable either by changing the color of the tooltip background on mouse over, or put an x in the top right?

Related open issues:

• #189 (closed) inform user when there may be a system-wide network connectivity issue
• #280 automated error recovery actions
• #311 (closed) suppress error responses for API calls which pertain to resources that we have already requested to delete
• #344 (closed) "Copy error text" button in Messages view
• #474 (closed) Proactively detect and correct problems
• #404 (closed) Better communication if Guacamole fails to deploy for some reason
• #472 (closed) Don't surface errors for BadStatus 502 from the User Application Proxy when Guacamole is unreachable
• #393 Better error message when Exosphere is served to the browser without a Cloud CORS Proxy configured
• #504 (closed) De-duplicate toast messages
• #708 Problem: The messages view is overwhelming