CE: Unit test coverage for Output::prepare and Output::rebuildLayerStack

Also modifies ui::Transform(int) to take two extra optional parameters
to set the width/height to use (forwarded to ui::Transform::set())

Bug: 144116499
Test: atest libcompositionengine_test
Change-Id: Ifb972c2619af41cb3999c50c082bce20b422c1ea
diff --git a/libs/ui/Transform.cpp b/libs/ui/Transform.cpp
index 28c3f7b..85abb38 100644
--- a/libs/ui/Transform.cpp
+++ b/libs/ui/Transform.cpp
@@ -33,8 +33,8 @@
     : mMatrix(other.mMatrix), mType(other.mType) {
 }
 
-Transform::Transform(uint32_t orientation) {
-    set(orientation, 0, 0);
+Transform::Transform(uint32_t orientation, int w, int h) {
+    set(orientation, w, h);
 }
 
 Transform::~Transform() = default;