EC Timeout if it doesn't respond after 30 seconds (#4237)

* basic implementation

* using a decodable struct to interpret the widget message

* small code refactor/improvement

ElementX/Sources/Services/ElementCall/ElementCallWidgetDriverProtocol.swift

@@ -36,6 +36,7 @@ protocol ElementCallWidgetDriverProtocol {
                analyticsConfiguration: ElementCallAnalyticsConfiguration?) async -> Result<URL, ElementCallWidgetDriverError>
     
     /// Passes a message from the Widget to the SDK to handle, returning a Bool that represents whether or not the widget driver is still running.
+    @discardableResult
     func handleMessage(_ message: String) async -> Result<Bool, ElementCallWidgetDriverError>
 }