Adding support for calling into SystemNavigationGestureSettings

For taskbar pinning feasture we need to link user to navigation mode system settings,
this CL will create
- New NavigationModeSettingsActivity
- Intent Filter to invoke SystemNavigationGestureSettings

Test: Manual
Bug: 279069606
Flag: not needed
Change-Id: I55b47d158d18bcb075329f795f15b2e6fc2ea810

src/com/android/settings/Settings.java

@@ -135,6 +135,8 @@ public class Settings extends SettingsActivity {
     /** Activity for the regional preferences settings. */
     public static class RegionalPreferencesActivity extends SettingsActivity { /* empty */ }
     public static class KeyboardSettingsActivity extends SettingsActivity { /* empty */ }
+    /** Activity for the navigation mode settings. */
+    public static class NavigationModeSettingsActivity extends SettingsActivity { /* empty */ }
     public static class UserDictionarySettingsActivity extends SettingsActivity { /* empty */ }
     public static class DarkThemeSettingsActivity extends SettingsActivity { /* empty */ }
     public static class DisplaySettingsActivity extends SettingsActivity { /* empty */ }