Gracefully fallback to IPv4 when IPv6 connection fails

[DominikFickenwirth]

Describe the feature you'd like

When connecting to stream.mydomain.com, the logic (at least in my phone) seems to be(*):

• If an AAAA-Record was found, try IPv6 connection. If that fails, show an error.
• If no AAAA-Record was found, try IPv4 connection. If that fails, show an error.

It would be nice to gracefully fall back to IPv4, if IPv6 fails:

• If an AAAA-Record was found, try IPv6 connect.
• If that fails or if no AAAA-Record was found, try IPv4 connect.
• If that fails, show an error.

Remarks

(*) This assumption is based on the following findings:

• I have configured stream.mydomain.com with both an A-Record for IPv4 and an AAAA-Record for IPv6. Both addresses point to my NAS running on my home network (and are updated via DynDNS).
• Due to an error in my home network, the IPv6 of my NAS was no longer reachable over the Internet. This resulted in "Unable to reach server ..." errors in the "Connect to Server" screen of the Jellyfin Android app.
• After deleting the AAAA-Record from my DNS (i.e. only sending the IPv4 address via DynDNS), the Jellyfin Android app connected to my NAS as expected.
• Before and after deleting the AAAA-Record, the Jellyfin web client always worked fine via my phone's browser (since the browser does gracefully fall back to IPv4).

Other notes:

• I am aware, that the best solution would be to correct the unreachable AAAA-Record. However, this feature would reduce the "downtime" (from the app's perspective) to zero.
• This also applies to the Jellyfin Android TV app. (Should I duplicate this issue in that repo or do they share a common code base?)
• Issue Android APP won't connect to server when using domain #786 seems to have the same root cause.
• See also https://forum.jellyfin.org/t-solved-android-app-not-connecting-outside