Move SkGLContext and some GrGLInterface implementations to skgputest module

src/gpu/gl/debug/SkDebugGLContext.h

-/*
- * Copyright 2012 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#ifndef SkDebugGLContext_DEFINED
-#define SkDebugGLContext_DEFINED
-
-#include "gl/SkGLContext.h"
-
-class SkDebugGLContext : public SkGLContext {
-public:
-    ~SkDebugGLContext() override;
-
-    static SkDebugGLContext* Create() {
-        return new SkDebugGLContext;
-    }
-private:
-    void onPlatformMakeCurrent() const override {}
-    void onPlatformSwapBuffers() const override {}
-    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
-
-    SkDebugGLContext();
-};
-
-#endif