SF: Refactor Scheduler mock injection

Factor out TestableScheduler setup to TestableSurfaceFlinger,
and instantiate a VSyncModulator, since the std::optional may
be dereferenced in tests.

Bug: 123530318
Test: libsurfaceflinger_unittest
Change-Id: Ic7c95024e63d861c5c5c53e4973995a4fd83a7d8
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 0d9d7aa..5905ff6 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -204,6 +204,10 @@
     enum class TimerState { Reset, Expired };
     enum class TouchState { Inactive, Active };
 
+    // Used by tests to inject mocks.
+    Scheduler(std::unique_ptr<DispSync>, std::unique_ptr<EventControlThread>,
+              const scheduler::RefreshRateConfigs&);
+
     // Creates a connection on the given EventThread and forwards the given callbacks.
     sp<EventThreadConnection> createConnectionInternal(EventThread*, ResyncCallback&&,
                                                        ISurfaceComposer::ConfigChanged);