Add display finder DRM flow

... so that downstream devices of Cuttlefish that run without
Cuttlefish's config server can still initialize displays.

Eventually, we want to enable this on Cuttlefish as well once
Crosvm fully supports the display properties we use (it looks like
it doesn't support DPI and refresh rate yet).

Bug: b/239855014
Test: cvd start --gpu_mode=gfxstream
                --display0=width=320,height=480
                --display1=width=640,height=500
      `adb shell getprop | grep "hwcomposer"`
      (to confirm mode)
      `adb shell dumpsys SurfaceFlinger`
      (to confirm display props)
      and interact with all displays.
Test: cvd start --gpu_mode=guest_swiftshader
                --display0=width=320,height=480
                --display1=width=640,height=500
                --display2=width=700,height=700
                --display3=width=800,height=600
      `adb shell getprop | grep "hwcomposer"`
      (to confirm mode)
      `adb shell dumpsys SurfaceFlinger`
      (to confirm display props)
      and interact with all displays.
Change-Id: Ifff742e5fc3fe12a1d81d294882bbb3d8b1560d2
13 files changed