Move SkGLContext and some GrGLInterface implementations to skgputest module

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1815823002
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac-Clang-x86_64-Release-CMake-Trybot

Committed: https://skia.googlesource.com/skia/+/fe3456cb006110d045b26ff3f8681b893a757b58

Review URL: https://codereview.chromium.org/1815823002
diff --git a/tests/GrPorterDuffTest.cpp b/tests/GrPorterDuffTest.cpp
index 54fcfc1..566ec12 100644
--- a/tests/GrPorterDuffTest.cpp
+++ b/tests/GrPorterDuffTest.cpp
@@ -1147,8 +1147,8 @@
 DEF_GPUTEST(PorterDuffNoDualSourceBlending, reporter, /*factory*/) {
     GrContextOptions opts;
     opts.fSuppressDualSourceBlending = true;
-    GrContextFactory mockFactory(opts);
-    GrContext* ctx = mockFactory.get(GrContextFactory::kNull_GLContextType);
+    sk_gpu_test::GrContextFactory mockFactory(opts);
+    GrContext* ctx = mockFactory.get(sk_gpu_test::GrContextFactory::kNull_GLContextType);
     if (!ctx) {
         SkFAIL("Failed to create null context without ARB_blend_func_extended.");
         return;