Test/demonstrate workflow_engine_params

[david4096]

The default workflow engine params key allows a WES to tell a client what the default flags are when running a workflow, above and beyond what appears in the workflow descriptor. In practice, this is similar to the interaction of working with help messages from CLI applications.

First, one can request the default workflow engine params from a service. This returns the various flags and "other settings" an engine can take and their defaults.

The client can then construct a workflow_engine_params key in the WorkflowRequest that can override these defaults as necessary.

To close this, add code that returns the defaults from service info https://github.com/ga4gh/workflow-execution-service-schemas/blob/develop/openapi/workflow_execution_service.swagger.yaml#L384 . These should be read from the help message of the runner, or argparse if available!

Then, add the ability to read the workflow_engine_params from the request in the runner. https://github.com/ga4gh/workflow-execution-service-schemas/blob/develop/openapi/workflow_execution_service.swagger.yaml#L531

Add a test that shows the parameters being accepted in the request and passed down for execution. The workflow run itself can fail, as long as we show the parameters are modifiable and that the above interaction pattern can be carried out.