[sb] adjust paddings around new wifi/mobile icons

- Constrain the RAT height to 12sp
- 3sp of padding on the start/end of each icon group
- adjust the padding of the system icons container in all contexts
  (keyguard, home screen, shade header)
- ShadeHead.kt will be updated next

Test: manual (see screenshots)
Test: screenshot tests
Flag: com.android.settingslib.flags.new_status_bar_icons
Bug: 397936541
Change-Id: I2aec5ca6f38703314df442c79f9194c6794dd5d9