SF: Restructure OutputLayer creation to remove displayId argument

The existing code was explicitly passing the displayId when creating an
OutputLayer, so that a HWC2::Layer could be created if applicable.

This patch makes a quick adjustment to the code so that the
compositionengine::Display instance overrides the base createOutputLayer
logic to create the HWC2::Layer, as it knows the displayId itself.

This is a minor cleanup prior to moving computeVisibleLayers to the
Output class.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Test: go/wm-smoke
Bug: 121291683
Change-Id: Ic7224ba445084b833b8c344436397372b2153d42
diff --git a/services/surfaceflinger/tests/unittests/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 9e4d57e..20dfed6 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -814,9 +814,7 @@
 
         std::vector<std::unique_ptr<compositionengine::OutputLayer>> outputLayers;
         outputLayers.emplace_back(test->mDisplay->getCompositionDisplay()
-                                          ->getOrCreateOutputLayer(DEFAULT_DISPLAY_ID,
-                                                                   layer->getCompositionLayer(),
-                                                                   layer));
+                                          ->createOutputLayer(layer->getCompositionLayer(), layer));
 
         outputLayers.back()->editState().visibleRegion = Region(Rect(0, 0, 100, 100));
         outputLayers.back()->editState().outputSpaceVisibleRegion = Region(Rect(0, 0, 100, 100));