[torconnect] Add Internet connection error when network isn't reachable

In the user flows (about-torconnect-user-flows.png) and following the conversation in #40781 (comment 2772219), we decided that users who fail to connect to Tor and can't reach moat either should get redirected to an Internet connection error instead:

I think it would be useful to explain that the user should check for network/proxy issues and try again, before attempting to config a bridge? I could use some help with the wording though please.