Slightly reduce number of cfgs (#3071)

* Make Linux platforms less dependent on the root monitor handle

* Add various functions to the Wayland platform to reduce cfgs

* Don't use a cfg in listen_device_events

* Don't use a cfg in set_content_protected

* Fix instance of a target_os cfg

src/platform_impl/linux/x11/mod.rs

@@ -706,7 +706,15 @@ impl<T> EventLoopWindowTarget<T> {
         &self.xconn
     }
 
-    pub fn set_listen_device_events(&self, allowed: DeviceEvents) {
+    pub fn available_monitors(&self) -> impl Iterator<Item = MonitorHandle> {
+        self.xconn.available_monitors().into_iter().flatten()
+    }
+
+    pub fn primary_monitor(&self) -> Option<MonitorHandle> {
+        self.xconn.primary_monitor().ok()
+    }
+
+    pub fn listen_device_events(&self, allowed: DeviceEvents) {
         self.device_events.set(allowed);
     }