drm_hwcomposer: Rework KMS composition planner + plane sharing support

Rewrite Layer-to-Plane planner. Get rid of ~200 redundant lines of code
+ added plane sharing functionality.

Closes: drm-hwcomposer/drm-hwcomposer#11
Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
2 jobs for plane-sharing-support in 13 minutes and 23 seconds (queued for 4 seconds)