Warn for soon to be deprecated OS versions (#3413)

src/Runner.Worker/JobExtension.cs

@@ -127,6 +127,10 @@ namespace GitHub.Runner.Worker
                         }
                     }
 
+                    // Check OS warning
+                    var osWarningChecker = HostContext.GetService<IOSWarningChecker>();
+                    await osWarningChecker.CheckOSAsync(context, message.OSWarnings);
+
                     try
                     {
                         var tokenPermissions = jobContext.Global.Variables.Get("system.github.token.permissions") ?? "";