Switch from HIDL Composition type to AIDL

In preparation for adding a new Composition type which is only in AIDL.
This change is almost completely mechanical, and should have no impact
on behavior.

Bug: 193170859
Test: existing tests

Change-Id: I1f923fcc8d8e6dff388493a76e31d435638b5255
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 3f4d48b..31cdf0b 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -1037,7 +1037,8 @@
     // Returns true if the layer can draw shadows on its border.
     virtual bool canDrawShadows() const { return true; }
 
-    Hwc2::IComposerClient::Composition getCompositionType(const DisplayDevice&) const;
+    aidl::android::hardware::graphics::composer3::Composition getCompositionType(
+            const DisplayDevice&) const;
 
     /**
      * Returns an unsorted vector of all layers that are part of this tree.