[FEA]: message_type argument to DeserializeStage should be an enum

[dagardner-nv]

Is this a new feature, an improvement, or a change to existing functionality?

Improvement

How would you describe the priority of this feature request

High

Please provide a clear description of problem this feature solves

Currently the type for this argument is the class itself. However if it were an enum, then our CLI tool will be able to handle it as a CLI arg.

Describe your ideal solution

Refer to #1834

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct
• I have searched the open feature requests and have found no duplicates for this feature request

[dagardner-nv]

Closing as MultiMessage is slated for removal in 24.10