Construct topology graph

The graph is used by Input Manager.

1. Sort displays by position
2. Loop through the displays
3. Inside that loop, loop through the remaining displays

Include the density in the graph. Change the offset to be in dp as Input Manager can now do the conversion to px itself using the density.

Bug: 384668407
Test: DisplayTopologyTest, InputManagerServiceTests
Flag: com.android.server.display.feature.flags.display_topology
Change-Id: Ib6240bc4ae52349f3744d66864c94b562b8ed8d8