Added logic for limiting extra apps shortcut customization

When user customizes 10 app shortcuts, we no longer allow further custom
app shortcut customization.

Test: ShortcutHelperViewModelTest
Flag: com.android.systemui.extended_apps_shortcut_category
Fix: 405985619
Change-Id: I7483b9a80bf3841d4d833187e56f3e9239305903