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-vi/translations.xml

@@ -191,7 +191,6 @@
   <string name="common_advanced_settings">"Cài đặt nâng cao"</string>
   <string name="common_an_image">"một hình ảnh"</string>
   <string name="common_analytics">"Phân tích"</string>
-  <string name="common_android_fetching_notifications_title">"Đang đồng bộ thông báo…"</string>
   <string name="common_android_shortcuts_remove_reason_left_room">"Bạn rời phòng"</string>
   <string name="common_android_shortcuts_remove_reason_session_logged_out">"Bạn đã bị đăng xuất"</string>
   <string name="common_appearance">"Giao diện"</string>
@@ -235,6 +234,7 @@ Lý do: %1$s ."</string>
   <string name="common_failed">"Thất bại"</string>
   <string name="common_favourite">"Yêu thích"</string>
   <string name="common_favourited">"Được yêu thích"</string>
+  <string name="common_fetching_notifications_title_android">"Đang đồng bộ thông báo…"</string>
   <string name="common_file">"Tập tin"</string>
   <string name="common_file_deleted">"Tệp đã bị xóa"</string>
   <string name="common_file_saved">"Tệp đã được lưu"</string>