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/Test/L0/RunnerWebProxyL0.cs

@@ -16,7 +16,9 @@ namespace GitHub.Runner.Common.Tests
         private static readonly List<string> SkippedFiles = new List<string>()
         {
             "Runner.Common\\HostContext.cs",
-            "Runner.Common/HostContext.cs"
+            "Runner.Common/HostContext.cs",
+            "Runner.Common\\HttpClientHandlerFactory.cs",
+            "Runner.Common/HttpClientHandlerFactory.cs"
         };
 
         [Fact]