Use the API_URL and munge action URLs for GHES (#437)

* First pass at logic for GHES, not all correct

* Need to mock out file downloading

* Allowed for mocking of HTTP responses

* Added test for builtin GHES action download

* More tests

* Don't retry on action 404

* Remove commented out code

* Add a using statement back, because Windows

* Make windows happy again

* Another windows fix

* Always delete the cache since it isn't fully implemented

* Use RunnerService base class

* Add examples, update URL path

* Remove forceDotCom

* Fix a bug

* Remove a test that's no longer relevant

* PR feedback

* Add missing return

* More trace info

* Use the new agreed-upon format

* Use the auth token since we're hitting GHES directly

* Fixing tests on windows

* Fixed one more test

src/Runner.Worker/ActionNotFoundException.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Runtime.Serialization;
+
+namespace GitHub.Runner.Worker
+{
+    public class ActionNotFoundException : Exception
+    {
+        public ActionNotFoundException(Uri actionUri)
+            : base(FormatMessage(actionUri))
+        {
+        }
+
+        public ActionNotFoundException(string message)
+            : base(message)
+        {
+        }
+
+        public ActionNotFoundException(string message, System.Exception inner)
+            : base(message, inner)
+        {
+        }
+
+        protected ActionNotFoundException(SerializationInfo info, StreamingContext context)
+                : base(info, context)
+        {
+        }
+
+        private static string FormatMessage(Uri actionUri)
+        {
+            return $"An action could not be found at the URI '{actionUri}'";
+        }
+    }
+}