Fix ForegroundServiceDidNotStartInTimeException (#6470)

* Start the `FetchPushForegroundService ` in foreground ASAP. This is a first step to mitigate `ForegroundServiceDidNotStartInTimeException` being thrown.

* Don't stop the service immediately if it's running but not in foreground. Try waiting up to 5s for it to be in foreground.

libraries/push/api/src/main/kotlin/io/element/android/libraries/push/api/push/PushHandlingWakeLock.kt

@@ -22,5 +22,5 @@ interface PushHandlingWakeLock {
     /**
      * Release the wakelock. If no wakelock is associated with the key, this method does nothing.
      */
-    fun unlock()
+    suspend fun unlock()
 }