Encrypted state events prototype

[turt2live]

TBD

Proof of concept goal: Encrypted room name and topic.

[SimonBrandner]

How this could work is explained here

[turt2live]

Rough design principle for this issue is we can actually avoid both suggestions there after workshopping internally.

[turt2live]

Proposed design: matrix-org/matrix-spec-proposals#3414

This issue affects all of Element, so in my humble opinion, we should transfer this issue to element-meta.