Report failures to download artifacts as failures (#3860)

Previously, an artifact that failed to download might print like this:

```
(proj) pkg> instantiate
  Downloaded artifact: Example
  Downloaded artifact: Example
ERROR: Unable to automatically download/install artifact 'Example' from sources listed in ...
```

With this change, that becomes:

```
(proj) pkg> instantiate
     Failure artifact: Example
     Failure artifact: Example
ERROR: Unable to automatically download/install artifact 'Example' from sources listed in ...
```

src/Artifacts.jl

@@ -476,13 +476,20 @@ function with_show_download_info(f, io, name, quiet_download)
         fancyprint && print_progress_bottom(io)
         printpkgstyle(io, :Downloading, "artifact: $name")
     end
+    success = false
     try
-        return f()
+        result = f()
+        success = result === true
+        return result
     finally
         if !quiet_download
             fancyprint && print(io, "\033[1A") # move cursor up one line
             fancyprint && print(io, "\033[2K") # clear line
-            fancyprint && printpkgstyle(io, :Downloaded, "artifact: $name")
+            if success 
+                fancyprint && printpkgstyle(io, :Downloaded, "artifact: $name")
+            else
+                printpkgstyle(io, :Failure, "artifact: $name", color = :red)
+            end
         end
     end
 end