* Add 'send private read receipts' option in advanced settings
* Create `SessionPreferencesStore` that stores the settings for the current use separate from those of the app.
* Rename `PreferencesStore` to `AppPreferencesStore` to split the preferences.
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Co-authored-by: ElementBot <benoitm+elementbot@element.io>
* Integrate Element Call with widget API.
- Add `appconfig` module and extract constants that can be overridden in forks there.
- Add an Element Call feature flag, disabled by default.
- Refactor the whole `ElementCallActivity`, move most logic out of it.
- Integrate with the Rust Widget Driver API (note the Rust SDK version used in this PR lacks some needed changes to make the calls actually work).
- Handle calls differently based on `CallType`.
- Add UI to create/join a call.
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Co-authored-by: ElementBot <benoitm+elementbot@element.io>
