Allow to overwrite ACTIONS_RESULTS_URL environment variable

By introducing a new environment variable with the name of
CUSTOM_ACTIONS_RESULTS_URL, allowing users of that repo to overwrite the
ACTIONS_RESULTS_URL environment variable. It's required for cache v2
service.

Author: enescakir

src/Runner.Worker/Handlers/NodeScriptActionHandler.cs

@@ -72,11 +72,15 @@ public async Task RunAsync(ActionRunStage stage)
                 Environment["ACTIONS_ID_TOKEN_REQUEST_URL"] = generateIdTokenUrl;
                 Environment["ACTIONS_ID_TOKEN_REQUEST_TOKEN"] = systemConnection.Authorization.Parameters[EndpointAuthorizationParameters.AccessToken];
             }
-            if (systemConnection.Data.TryGetValue("ResultsServiceUrl", out var resultsUrl) && !string.IsNullOrEmpty(resultsUrl))
+            string customResultsUrl = System.Environment.GetEnvironmentVariable("CUSTOM_ACTIONS_RESULTS_URL");
+            if (!string.IsNullOrEmpty(customResultsUrl))
+            {
+                Environment["ACTIONS_RESULTS_URL"] = customResultsUrl;
+            }
+            else if (systemConnection.Data.TryGetValue("ResultsServiceUrl", out var resultsUrl) && !string.IsNullOrEmpty(resultsUrl))
             {
                 Environment["ACTIONS_RESULTS_URL"] = resultsUrl;
             }
-
             if (ExecutionContext.Global.Variables.GetBoolean("actions_uses_cache_service_v2") ?? false)
             {
                 Environment["ACTIONS_CACHE_SERVICE_V2"] = bool.TrueString;