Implement workflow actions

[adhityamamallan]

Summary

• Extend the WorkflowAction type to depend on a result type (we'll need to do something similar for input too)
• Add fields:
  • apiRoute: the route handler URL
  • getSuccessMessage: success message to show in snackbar after action succeeds
• Add snackbar to Workflow Actions view to handle success notifications
• Move modal content to separate file
• Invoke actions using useMutation
• Update configs with new values

Test plan

Added unit tests + ran locally.

Cancellation:

Failure to terminate:

[adhityamamallan]

I'll put it back up for review once #791 is merged