Move utility classes in a separate static target

Split up utility classes that can be re-used in other IComposer related
tests (such as the IVrComposerClient tests).

Changes:
 * Move GraphicsComposerCallback into separate module
 * Extract TestCommandReader in separate module
 * Extract Composer::execute() from test class

Bug: 38203529
Test: Compiled
Change-Id: I0d1193469e9dd94c477a63058f98111c162dfa99
diff --git a/graphics/composer/2.1/vts/functional/VtsHalGraphicsComposerTestUtils.h b/graphics/composer/2.1/vts/functional/VtsHalGraphicsComposerTestUtils.h
index 4b57264..4e69f61 100644
--- a/graphics/composer/2.1/vts/functional/VtsHalGraphicsComposerTestUtils.h
+++ b/graphics/composer/2.1/vts/functional/VtsHalGraphicsComposerTestUtils.h
@@ -23,9 +23,12 @@
 #include <unordered_set>
 #include <vector>
 
+#include <IComposerCommandBuffer.h>
 #include <android/hardware/graphics/composer/2.1/IComposer.h>
 #include <utils/StrongPointer.h>
 
+#include "TestCommandReader.h"
+
 namespace android {
 namespace hardware {
 namespace graphics {
@@ -44,6 +47,7 @@
 class Composer {
  public:
   Composer();
+  explicit Composer(const std::string& name);
 
   sp<IComposer> getRaw() const;
 
@@ -102,6 +106,8 @@
   void setPowerMode(Display display, IComposerClient::PowerMode mode);
   void setVsyncEnabled(Display display, bool enabled);
 
+  void execute(TestCommandReader* reader, CommandWriterBase* writer);
+
  private:
   sp<IComposerClient> mClient;