Rename "complete-task" to "start-worker"

[pihme]

Is your feature request related to a problem? Please describe.
The action "complete-task" is misleading. It sounds as if I could complete a single activated job. However, what is actually happening is that a worker is started which is waiting for jobs to get activated and then completing all of them.

Describe the solution you'd like
I would like to have a name that is clear.

[pihme]

I'm happy to make the change. I just wanted to create the issue as a reminder, so we can talk about and decide whether this shall be changed or not.

[saig0]

I'm supporting the intention of having clear names. When we talk about Zeebe then it would be more exact to call it "start-worker".

But I'm not sure about changing the name because the tool should be agnostic to the concrete BPMN engine. Another engine may call it differently. The name "complete-task" is more general. So, the concrete test runner can implement it in a proper way.