Allow template refs to validate against original WorkflowTemplate

[elliotgunton]

Is your feature request related to a problem? Please describe.
TemplateRefs do not do any validation on the input parameters, so you will only find out when linting or submitting the workflow.

Describe the solution you'd like

• Generate stubs (through the CLI) to use them in the same way as for decorator-based workflows.

Describe alternatives you've considered

• Something like a new custom TemplateRef Hera class to create the stubs manually

Additional context
Add any other context or screenshots about the feature request here.

• Pulling out the "stub gen" part of the Hera CLI design #670
• Will expand on the implementation details when I have time