Separate permissions for integrated Jitsi from integration manager widgets

I think it would be good to differentiate regarding the room permissions for the integrated Jitsi and the room permissions called `Modify Widgets` …

Regular users should be able to start a Jitsi call, if allowed to do so, but that should not give them access to any widgets from the integration manager.

The issue names integrated Jitsi permissions and the integration manager's “Modify Widgets” permission, but provides no files, tests, or entry points. Start by locating those permission definitions in the relevant Element clients and clarify the intended separation; done means Jitsi calls and widget modification can be granted independently.

Written by the indexing model from the issue text.