DisplayTopology: keep nodes' logical width/height

This causes most backing fields to be int's rather than floats. The
device-independent pixels are calculated on-the-fly.

When updating the wallpaper previews in the topology pane, we need to
know the physical size of the wallpaper, and to avoid another fetch for
every displays' DisplayInfo data, I considered adding it to the
topology info.

Flag: com.android.settings.flags.display_topology_pane_in_display_list
Test: atest (modified tests)
Test: new test DisplayTopologyTest.rearrange_variousDensities
Bug: b/397231553
Bug: b/407028459
Change-Id: I02601016880629d6e7fe015b4ff889e8b69dd792