SF: Encapsulate frame targeting

Introduce FrameTargeter to isolate a display's per-frame metrics around
past/upcoming deadline targets. The Scheduler updates the FrameTargeter
on frame begin/end, whereas ICompositor (concretely SurfaceFlinger) has
read-only access via the FrameTarget interface.

For now, only instantiate the pacesetter's FrameTargeter.

The only functional change is that `earliestPresentTime` now takes into
account the case of targeting two VSYNCs ahead.

Bug: 241285475
Bug: 241285191
Test: Perfetto
Test: dumpsys SurfaceFlinger --scheduler
Test: atest libscheduler_test:FrameTargeterTest
Change-Id: Idf9f43b37f3479c94a478d154eaa46f43e0c6c9d
diff --git a/services/surfaceflinger/tests/unittests/TestableScheduler.h b/services/surfaceflinger/tests/unittests/TestableScheduler.h
index 3b6a987..5d2dfe4 100644
--- a/services/surfaceflinger/tests/unittests/TestableScheduler.h
+++ b/services/surfaceflinger/tests/unittests/TestableScheduler.h
@@ -166,8 +166,8 @@
 private:
     // ICompositor overrides:
     void configure() override {}
-    bool commit(TimePoint, VsyncId, TimePoint) override { return false; }
-    void composite(TimePoint, VsyncId) override {}
+    bool commit(const scheduler::FrameTarget&) override { return false; }
+    CompositeResult composite(scheduler::FrameTargeter&) override { return {}; }
     void sample() override {}
 };