Regression: Embedded mode no longer works with widget host that does not support update_state action

[hughns]

#4574 landed via bdd4d82 into the RCs for v36.1.0.

The problem is that if the widget host doesn't support the new update_state action then the fetching of room state will never work. For example, the matrix-rust-sdk does not support update_state yet.

This will impact any widget that uses the matrix-js-sdk in embedded mode including element-call.

A proposed fix is in #4652

I've marked this as a release blocker as it wasn't intended that this would be incompatible.

[hughns]

A proposed fix is in #4652

Rolling this change back would also be acceptable from VoIP team point of view.

[hughns]

n.b. because EW/ED doesn't use the embedded mode this isn't a blocker for those upstream clients. Instead it is an issue for any downstream consumers of js-sdk.

[hughns]

After discussion with web team I've prepared a revert so that we don't need to delay the current release cycle.