Introduce isApplyInProgress data flow

If isApplyInProgress true, isApplyButtonEnabled will be false which
prevent us from 2 cases
1. User clicks the enabled apply button again
2. Discard dialog pops up when on complete and the system setting is yet
   fully complete

Test: Manually tested that discard dialog does not pop up
Bug: 409895694
Flag: com.android.systemui.shared.new_customization_picker_ui
Change-Id: I995b128e575eaa4121d86c51137395a18366e117