Move SkGLContext and some GrGLInterface implementations to skgputest module

gm/image.cpp

Index: gm/image.cpp
diff --git a/gm/image.cpp b/gm/image.cpp
index c86be079d95727e879d1e04a3409017f1e6ba761..ab3ea2e5ae8651384f805c10e492e3f4baa02c50 100644
--- a/gm/image.cpp
+++ b/gm/image.cpp
@@ -433,7 +433,7 @@ DEF_SIMPLE_GM(new_texture_image, canvas, 225, 60) {
     GrContext* context = nullptr;
 #if SK_SUPPORT_GPU
     context = canvas->getGrContext();
-    GrContextFactory factory;
+    sk_gpu_test::GrContextFactory factory;
 #endif
     if (!context) {
         skiagm::GM::DrawGpuOnlyMessage(canvas);