The old "unwind tip" was removed in #738

[Kani] info: Verification output shows one or more unwinding failures.
[Kani] tip: Consider increasing the unwinding value or disabling

We should re-introduce this tip using the new output parsing/formatting code instead of the old "grep" mechanism.

We should also add tips based on other detectable error conditions, at least:

• Unwind
• If we see an assertion failure on an unsupported feature.
• Undefined function (detect std:: or core:: and advise for now too?)
• Maybe we can clean up some of those "internal sanity check" assertions that direct people to open bugs with us
• Others? (edit to add them?)