[Status Bar Refactor] 2/3: Remove

HeadsUpAppearanceController#readFrom(oldController).

Instead, the old values are read from the parent controllers. This CL
plus the next CL will allow us to not keep track of old
HeadsUpAppearanceController instances; instead, each
HeadsUpAppearanceController knows how to correctly set itself up and
tear itself down without needing the old controller.

Bug: 205609837
Test: atest SystemUITests
Test: manual (verified via logging that new controller gets old values)
Change-Id: I15adc79982b5b7ca264e2bb45e92ba48b9844c1a