Improve Email Changed form user feedback

My only UX feedback is that after clicking 'save' on the user form, the email reverts to the old email and a few beats later you get the toast notification saying to check your email to verify. It might be nice to add a message inline to the form... but not going to hold this up for that.

_Originally posted by @knolleary in https://github.com/flowforge/flowforge/pull/1954#pullrequestreview-1380983259_