Draft: fixup! Bug 41075: Accept self-signed certificates for onion services

Addressing "The Tor Browser is showing caution sign but your document said it won't" #41075 (closed)

Create a new error that signals a self signed cert exists, but since this is an onion connection, it is ignorable. Don't set errors in this case that would terminate the ssl connection. Then handle showing secure connection panel with self signed cert.