Move FlagManager to a common SF lib

So that CompositionEngine can use it.

Bug: 236745178
Test: builds
Change-Id: Ib873cb4a0b4231723a22fbc8fa22ec955aa6f329
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 9c8555e..7333bc3 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -113,6 +113,7 @@
 #include <unordered_map>
 #include <vector>
 
+#include <common/FlagManager.h>
 #include <gui/LayerStatePermissions.h>
 #include <gui/SchedulingPolicy.h>
 #include <ui/DisplayIdentification.h>
@@ -129,7 +130,6 @@
 #include "DisplayHardware/VirtualDisplaySurface.h"
 #include "DisplayRenderArea.h"
 #include "Effects/Daltonizer.h"
-#include "FlagManager.h"
 #include "FpsReporter.h"
 #include "FrameTimeline/FrameTimeline.h"
 #include "FrameTracer/FrameTracer.h"