Store the built-in bridges in OnionShare settings as a dict, and try writing those into the torrc if present.
If they aren't present in OnionShare settings, use the hardcoded templates instead.
Fetch the latest built-in bridges over Tor, once connected to Tor.
If we can't fetch the bridges over Tor, fall back to Meek (domain-fronting) and try again.
Then write those as the dict to the OnionShare settings, to take precedence next time.
