SF: Separate SurfaceInterceptor into interface and impl

SurfaceInterceptor is now an abstract interface.
impl::SurfaceInterceptor is the normal implementation.

This allows unit tests to replace it with a GMock.

Test: Builds
Bug: 74827900
Change-Id: I4d5bb2649b0c7a8ec1e6c0abf01ab53174d06a19
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 3671a2b..84fb827 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -66,6 +66,10 @@
 class LayerDebugInfo;
 class LayerBE;
 
+namespace impl {
+class SurfaceInterceptor;
+}
+
 // ---------------------------------------------------------------------------
 
 struct CompositionInfo {
@@ -583,7 +587,7 @@
 
     virtual void onFirstRef();
 
-    friend class SurfaceInterceptor;
+    friend class impl::SurfaceInterceptor;
 
     void commitTransaction(const State& stateToCommit);