Convert DisplayList to a value-type wrapper

Make DisplayList its own type instead of an alias,
pushing the Skia aspect behind it mostly. Removes a bunch
of manual memory management and opens the door to DisplayList
being a union type with multiple implementations

Test: builds (somehow), boots, hwuiunit passes, CtsUiRendering passes
Change-Id: I1d7806aa3afc5d9ece08b06959920078a5814c59
diff --git a/libs/hwui/tests/unit/RenderNodeTests.cpp b/libs/hwui/tests/unit/RenderNodeTests.cpp
index 4659a92..61bd646 100644
--- a/libs/hwui/tests/unit/RenderNodeTests.cpp
+++ b/libs/hwui/tests/unit/RenderNodeTests.cpp
@@ -326,7 +326,7 @@
 
     // Check that the VD is in the dislay list, and the layer update queue contains the correct
     // damage rect.
-    EXPECT_TRUE(rootNode->getDisplayList()->hasVectorDrawables());
+    EXPECT_TRUE(rootNode->getDisplayList().hasVectorDrawables());
     ASSERT_FALSE(info.layerUpdateQueue->entries().empty());
     EXPECT_EQ(rootNode.get(), info.layerUpdateQueue->entries().at(0).renderNode.get());
     EXPECT_EQ(uirenderer::Rect(0, 0, 200, 400), info.layerUpdateQueue->entries().at(0).damage);