introduce localtemp (temp files that shall end up on local storage and lead to auto-grouping like pipe output does)

https://github.com/snakemake/snakemake/blob/359ae2e17f31f33ba8059d75239c0e064bbd7520/snakemake/dag.py#L1716

https://github.com/snakemake/snakemake/blob/359ae2e17f31f33ba8059d75239c0e064bbd7520/snakemake/dag.py#L678