Add "DownloadManagement" app feature for use in NativeShell clients (#6833)

* Add "DownloadManagement" app feature for use in NativeShell clients

* Address review feedback

* Address review feedback (round 2)

src/constants/appFeature.ts

@@ -10,6 +10,8 @@ export enum AppFeature {
     DisplayLanguage = 'displaylanguage',
     /** The app supports configuring the display mode (TV, Desktop, etc.) */
     DisplayMode = 'displaymode',
+    /** The app supports showing a download management interface via a menu entry */
+    DownloadManagement = 'downloadmanagement',
     /** The app can exit via back navigation */
     Exit = 'exit',
     /** The app can be exited via a menu entry */