Speed up waitForToastMessageGone, handle error case

[w33ble]

Merge #5488 first

While working on the tryForTime change, I happened across another random functional test failure. Leadfoot's findAllByCssSelector apparently can either resolve with an empty array or reject, and there's seemingly no simple way to check for which will happen.

• Adds a catch handler to waitForToastMessageGone
• Speeds up the timeout in waitForToastMessageGone
• Adds some additional debugging