SurfaceFlinger: Remove removeLayer

We remove explicit layer destruction and replace it
with reparent->null, completing the transition to
a reference counted model.

Test: Manual
Bug: 62536731
Bug: 111373437
Bug: 111297488

Change-Id: I8ac7c5c5125e1c8daf84b42db00e1dd93a544bb5
diff --git a/services/surfaceflinger/tests/Stress_test.cpp b/services/surfaceflinger/tests/Stress_test.cpp
index 3e1be8e..89c26f4 100644
--- a/services/surfaceflinger/tests/Stress_test.cpp
+++ b/services/surfaceflinger/tests/Stress_test.cpp
@@ -34,7 +34,7 @@
             auto surf = client->createSurface(String8("t"), 100, 100,
                     PIXEL_FORMAT_RGBA_8888, 0);
             ASSERT_TRUE(surf != nullptr);
-            client->destroySurface(surf->getHandle());
+            surf->clear();
         }
     };