[Dual Shade] Add ShadeConfigRepository.

The ShadeConfigRepository, and the underlying config resources, will
consolidate the currently-scattered set of shade behavior decisions
across the different form factors and product types.

As a first example of usage, this CL consolidates one such piece of
behavior: the decision whether to layout the Dual Shade full-width or
floating.

Bug: 444424242
Test: Manually tested by opening the shade on a device with different
 configurations (portrait/landscape phone, portrait/landscape folable)
 and observing the shade renders correctly.
Test: Updated unit tests.
Flag: com.android.systemui.scene_container
Change-Id: I791696badf25514c5dbf3418964af1efb0afcac0