drm_hwcomposer: Make flattening thread-based instead of vsync-based

Using vsync means consume some CPU time every frame for
IRQ -> Kernel_Thread -> UserSpace_listener thread transitions.

Framework tries to reduce vsync usage to the minimum, by using timelines
instead.

New flattening controller thread wakes-up only once per second.

This commit also removes flattening info from dumpsys. Practice shows
that it is almost useless. Instead debugging can be done using ALOGV
dumps.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/Android.bp b/Android.bp
index 1e78729..0e313ea 100644
--- a/Android.bp
+++ b/Android.bp
@@ -59,6 +59,7 @@
         "bufferinfo/BufferInfoMapperMetadata.cpp",
 
         "compositor/DrmKmsPlan.cpp",
+        "compositor/FlatteningController.cpp",
 
         "drm/DrmAtomicStateManager.cpp",
         "drm/DrmConnector.cpp",