Add activities to handle external storage intents

Adds 2 activities with the appropriate intent-filters to handle intents
used to control OP_MANAGE_EXTERNAL_STORAGE:
* Generic activity to handle ACTION_MANAGE_ALL_FILES_ACCESS_PERMISSION
  which control all apps (that request MANAGE_EXTERNAL_STORAGE).
* App specific activity to handle
  ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION. The intent filter
  expects the name of the package as data in the intent.

Test: manual
Bug: 146425146
Change-Id: Iebc7d153eac6ffe0b9bd75196bc8ecf9cb687939

src/com/android/settings/Settings.java

@@ -139,6 +139,7 @@ public class Settings extends SettingsActivity {
     public static class AppMemoryUsageActivity extends SettingsActivity { /* empty */ }
     public static class OverlaySettingsActivity extends SettingsActivity { /* empty */ }
     public static class ManageExternalStorageActivity extends SettingsActivity { /* empty */ }
+    public static class AppManageExternalStorageActivity extends SettingsActivity { /* empty */ }
     public static class WriteSettingsActivity extends SettingsActivity { /* empty */ }
     public static class ChangeWifiStateActivity extends SettingsActivity { /* empty */ }
     public static class AppDrawOverlaySettingsActivity extends SettingsActivity { /* empty */ }