Improve FetchPushForegroundService's reliability (#6757)

* Improve `FetchPushForegroundService`'s reliability

- Don't use DI, we can just create the notification channel. This should speed up the creation of the service and reduce the number of `ForegroundServiceDidNotStartInTimeException` received. Also use `MainScope` instead of the app's coroutine scope.
- Move the wakelock releasing mechanism to `onDestroy` so it's always used. Previously, this would only happen when `stopService` was called, which would only happen when `stopSelf()` is called, but not when the OS or the service manager stops the service.

* Add fallback value for the notification channel title

* Replace the wrong string for the notification/channel title

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Co-authored-by: Benoit Marty <benoitm@element.io>

libraries/ui-strings/src/main/res/values-pl/translations.xml

@@ -201,7 +201,6 @@
   <string name="common_advanced_settings">"Ustawienia zaawansowane"</string>
   <string name="common_an_image">"obraz"</string>
   <string name="common_analytics">"Dane analityczne"</string>
-  <string name="common_android_fetching_notifications_title">"Synchronizuję powiadomienia…"</string>
   <string name="common_android_shortcuts_remove_reason_left_room">"Opuściłeś pokój"</string>
   <string name="common_android_shortcuts_remove_reason_session_logged_out">"Zostałeś wylogowany z sesji"</string>
   <string name="common_appearance">"Wygląd"</string>
@@ -247,6 +246,7 @@ Powód: %1$s."</string>
   <string name="common_failed">"Niepowodzenie"</string>
   <string name="common_favourite">"Ulubione"</string>
   <string name="common_favourited">"Ulubione"</string>
+  <string name="common_fetching_notifications_title_android">"Synchronizuję powiadomienia…"</string>
   <string name="common_file">"Plik"</string>
   <string name="common_file_deleted">"Plik usunięty"</string>
   <string name="common_file_saved">"Plik zapisany"</string>