New keyword: `Fetch and pass` - Pass Execution if no workload fetched

We often have a task template like this:

```robot
*** Settings ***
Library CamundaLibrary ${CAMUNDA_HOST}

*** Variables ***
${CAMUNDA_HOST} %{CAMUNDA_HOST}
${BATCH_SIZE} %{BATCH_SIZE}

*** Tasks ***
Run Robot Service Task
FOR ${i} IN RANGE 0 ${BATCH_SIZE}
${workload} fetch workload my_task_topic_name
${fetched_process_instance} Get fetch response
Pass execution if not $fetched_process_instance Finshed processing ${i} process instances
do something with workload ${workload}
END
```

It would be nice, if condition for ending the task and fetching could be combined:

```robot
*** Tasks ***
Run Robot Service Task
FOR ${i} IN RANGE 0 ${BATCH_SIZE}
${workload} fetch and pass my_task_topic_name message=Finshed processing ${i} process instances
do something with workload ${workload}
END
```

Start by locating the existing `fetch workload` and `Pass execution if` keywords in the Python library. Review how their arguments and return values are handled, then define the combined `fetch and pass` behavior shown in the issue. Done means the new keyword fetches the workload and passes execution with the supplied message when no workload is fetched.

Written by the indexing model from the issue text.