Add WhatsApp-style mode for all E2EE stuff, that auto-generate and auto-sign all requests without any questions to user

Most of Riot users don't understand, why setting up encryption in it is so hard, and why in WhatsApp-like messengers E2EE works out-of-the-box, without creating password, confirming users, cross-signing, etc.

Explanations like "In WhatsApp this done via bad way, in Riot - via good way" don't help, most of users select way "Not to use so complicated Riot, but continue talking in WhatsApp", that's bad!

Solution for this can be implementing "WhatsApp-style mode for all E2EE stuff", that will auto-generate password for SSSS, auto-sign all keys and requests without any questions, and for initial encryption setup dialog add button "Ignore all encryption" with description why this is bad solution.