Ensure that a PushProvider is available on a device before using it.

It help to fallback to UnifiedPush (if available) if the PlayServices are not installed on the device.

libraries/push/impl/src/main/kotlin/io/element/android/libraries/push/impl/DefaultPushService.kt

@@ -38,7 +38,9 @@ class DefaultPushService @Inject constructor(
     }
 
     override fun getAvailablePushProviders(): List<PushProvider> {
-        return pushProviders.sortedBy { it.index }
+        return pushProviders
+            .filter { it.isAvailable() }
+            .sortedBy { it.index }
     }
 
     /**