Remove argument separator from commands (#5080)

* Remove argument separator from commands

Currently, the argument separator (`--`) is only supported on
`dotnet run`. This PR removes it from other commands to make the help and
usage of these command clearer.

* Adding dotnet run message test

* Responding to PR feedback

src/dotnet/commands/dotnet-publish/Program.cs

@@ -17,7 +17,7 @@ namespace Microsoft.DotNet.Tools.Publish
             app.Name = "dotnet publish";
             app.FullName = LocalizableStrings.AppFullName;
             app.Description = LocalizableStrings.AppDescription;
-            app.AllowArgumentSeparator = true;
+            app.HandleRemainingArguments = true;
             app.ArgumentSeparatorHelpText = HelpMessageStrings.MSBuildAdditionalArgsHelpText;
             app.HelpOption("-h|--help");