Use timestamp instead of frame number when generating test pattern.

Frame number is reset upon reconfiguration and causes test pattern
to be generated from point 0 as well.

Bug: 301023410
Test: manually with OpenCamera
Change-Id: Ib037293117b8ce4f143af2d36fa6aa94845c5efb
diff --git a/services/camera/virtualcamera/VirtualCameraTestInstance.cc b/services/camera/virtualcamera/VirtualCameraTestInstance.cc
index bae871d..1eac4fe 100644
--- a/services/camera/virtualcamera/VirtualCameraTestInstance.cc
+++ b/services/camera/virtualcamera/VirtualCameraTestInstance.cc
@@ -107,7 +107,7 @@
     }
 
     // Render the test pattern and update timestamp.
-    testPatternProgram.draw(frameNumber++);
+    testPatternProgram.draw(ts);
     eglDisplayContext.swapBuffers();
     lastFrameTs = getCurrentTimestamp();
   }