Rename GrDrawingMgr::abandon to wasAbandoned & add a matching entry point to GrDrawingContext

Since GrDrawingContext is generally replacing GrRenderTarget, this is to provide functionality similar to GrRenderTarget::wasDestroyed.

This is split out of https://codereview.chromium.org/1930013002/ ((Mostly) Retract GrRenderTarget from SkGpuDevice)

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1979913002

Review-Url: https://codereview.chromium.org/1979913002
diff --git a/include/gpu/GrDrawContext.h b/include/gpu/GrDrawContext.h
index 1ffa987..7409da3 100644
--- a/include/gpu/GrDrawContext.h
+++ b/include/gpu/GrDrawContext.h
@@ -264,6 +264,8 @@
     int numColorSamples() const { return fRenderTarget->numColorSamples(); }
     bool isGammaCorrect() const { return fSurfaceProps.isGammaCorrect(); }
 
+    bool wasAbandoned() const;
+
     GrRenderTarget* accessRenderTarget() { return fRenderTarget.get(); }
 
     sk_sp<GrRenderTarget> renderTarget() { return fRenderTarget; }