Add debug flag for App Settings page

Default no-op, if SETTINGS_ENABLE_SPA is enabled, InstalledAppDetailsTop
will navigate to SPA AppSettings instead of AppInfoDashboardFragment.

Bug: 236346018
Test: Manual with Settings App
Change-Id: I0b8a668df1f8783b860baae1d912157f742baf3f

src/com/android/settings/spa/app/appsettings/AppSettings.kt

@@ -60,6 +60,13 @@ object AppSettingsProvider : SettingsPageProvider {
 
     @Composable
     fun navigator(app: ApplicationInfo) = navigator(route = "$name/${app.toRoute()}")
+
+    /**
+     * Gets the route to the App Settings page.
+     *
+     * Expose route to enable enter from non-SPA pages.
+     */
+    fun getRoute(packageName: String, userId: Int): String = "$name/$packageName/$userId"
 }
 
 @Composable