External display hotplug support v3

V3:

• Rebased onto the master
• Comments from @seanpaul were addressed

V2:

• Rebased onto the master
• Minor fixes after testing on real hardware
• Some of the comments from @seanpaul were addressed
• Additional patch for the preferred mode

V1:

First of all, you need to have these patches(not a part of 8 and 8.1) in the Android tree for correct hotplug:

https://android-review.googlesource.com/c/platform/frameworks/native/+/613509/2

https://android-review.googlesource.com/c/platform/frameworks/native/+/613510/2

https://android-review.googlesource.com/c/platform/frameworks/native/+/613511/3

Open questions for now: Do we need hotplug of main display?

Can somebody test these on the real hardware? (I'm working in a hypervisor environment, so I unable to test these on real hardware).

Comments are highly appreciated.