Run number determination in `xtl.autoproc process_wf`

[dtriand]

If the output directory for a dataset already contains a previous xtl.autoproc process_wf run (e.g. autoproc_wf_run01), then rerunning the command fails to recognize the existing run, thus does not increment the run number and attempts to rerun in the same directory, resulting in funny autoPROC errors. Potentially an issue with AutoPROCWorkflowJob._job_prefix and inheritance?