[Spa] Polish CustomizedAppBar

- The padding logic better to be part of CustomizedAppBar, instead of
  BackAction
- Paddings polished
- Remove toSemiBoldWeight(), set FontWeight.SemiBold directly to
  Emphasized styles, which can also apply to languages as Chinese
- Fix an issue that when return from other page, the CustomizedAppBar
  collapse again

Bug: 419002002
Flag: EXEMPT bug fix
Test: visual
Change-Id: I7d029be278972ad797fb598c82550bd814579ed8