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

Review URL: https://codereview.chromium.org/1815823002
diff --git a/tests/skia_test.cpp b/tests/skia_test.cpp
index 5d21d1e..9783db8 100644
--- a/tests/skia_test.cpp
+++ b/tests/skia_test.cpp
@@ -24,6 +24,7 @@
 #endif
 
 using namespace skiatest;
+using namespace sk_gpu_test;
 
 DEFINE_bool2(extendedTest, x, false, "run extended tests for pathOps.");