Add plugin task type inference workflow

[keithmanville]

Add a new workflow endpoint for inferring the types of a plugin task.

POST /workflows/pluginTaskInfer {"plugin_file": "contents"}

The response should be something like:

{
  task_name: {
    "inputParams": { name: inferredType, ... } }, 
    "outputParams": [inferredType, ...] }
   }, ...
}

This feature should build off of #443

Definition of Done

• Signature analysis functionality is added
• A new workflow that uses the signature analysis functionality is added
• New tests are added for this workflow
• All tests pass
• The feature is merged into dev