SF: Bundle ftl::Flags for CompositionCoverage

...as they will later be passed to Scheduler via ICompositor. For now,
extract ICompositor to its own header, alongside CompositionCoverage.

Bug: 241285475
Bug: 241285191
Test: Frame misses are still traced.
Change-Id: I1562893c9357a02aa42516e775700065b9b17e4b
diff --git a/services/surfaceflinger/Scheduler/MessageQueue.h b/services/surfaceflinger/Scheduler/MessageQueue.h
index ad0ea72..0d59337 100644
--- a/services/surfaceflinger/Scheduler/MessageQueue.h
+++ b/services/surfaceflinger/Scheduler/MessageQueue.h
@@ -37,15 +37,7 @@
 
 namespace android {
 
-struct ICompositor {
-    virtual void configure() = 0;
-    virtual bool commit(TimePoint frameTime, VsyncId, TimePoint expectedVsyncTime) = 0;
-    virtual void composite(TimePoint frameTime, VsyncId) = 0;
-    virtual void sample() = 0;
-
-protected:
-    ~ICompositor() = default;
-};
+struct ICompositor;
 
 template <typename F>
 class Task : public MessageHandler {