feat: Enable Webxdc realtime by default

[Hocuri]

Mainly after discussions between @hpk42, @r10s, and @adbenitez.

Todo for the UIs:

• Move the option from experimental to a normal advanced setting.

Considerations:

• if someone ants to get your IP address, they can just send you a link to some server where they can look into the log files
  • So, opening a Webxdc is similar to sending a link
• Your chat partner will have to modify their DC app or monitor network traffic to actually see your IP address

Open questions:

• Should this PR wait until all the UIs moved the option from "experimental" to a normal advanced setting?

Future possibilities:

• Add a button the UI "set all settings to be maximally secure" or similar that disables this and other settings

[adbenitez]

• off-topic: I think we should rename private apps to mini-apps, noone knows what private apps are)

+1 it is better to use a well know term and then explain "Delta Chat mini-apps are better/more-secure than X" than using a new term