Remove SkAutoTUnref and SkAutoTDelete from public includes.

This also makes the required changed to src, tests, and tools. The few
public APIs modified by this change appear to be unused outside of Skia.

Removing these from the public API makes it easier to ensure users are
no longer using them.

This also updates GrGpu::wrapBackendXXX and the
::onWrapBackendXXX methods to clarify ownership.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2448593002

Review-Url: https://codereview.chromium.org/2448593002
diff --git a/tests/ImageTest.cpp b/tests/ImageTest.cpp
index e7de369..a0ce16f 100644
--- a/tests/ImageTest.cpp
+++ b/tests/ImageTest.cpp
@@ -889,7 +889,7 @@
 DEF_GPUTEST_FOR_RENDERING_CONTEXTS(DeferredTextureImage, reporter, ctxInfo) {
     GrContext* context = ctxInfo.grContext();
     sk_gpu_test::TestContext* testContext = ctxInfo.testContext();
-    SkAutoTUnref<GrContextThreadSafeProxy> proxy(context->threadSafeProxy());
+    sk_sp<GrContextThreadSafeProxy> proxy = context->threadSafeProxy();
 
     GrContextFactory otherFactory;
     ContextInfo otherContextInfo =