SF: Store DeviceProductInfo in DisplayDeviceState

After a hotplug we store DeviceProductInfo in
DisplayDeviceState, so it can be used later without calling
into HardwareComposer and parsing the EDID.

Bug: 149075047
Test: atest libsurfaceflinger_unittest
Test: 1. flash a device
      2. boot a device connected to a display
      3. Check for sensible DeviceProductInfo:
         adb shell dumpsys SurfaceFlinger | grep deviceProductInfo
         adb shell dumpsys display | grep deviceProductInfo
      4. reboot without a display
      5. Check that  DeviceProductInfo is empty / null in
         adb shell dumpsys SurfaceFlinger | grep deviceProductInfo
         adb shell dumpsys display | grep deviceProductInfo
Change-Id: Ide3354c1779c2ced88954c7b50e5500568d8482b