Support for gzipped FASTQ input in `sc_atac_preprocess`

[Billsfriend]

Hello,

I’ve noticed that during the sc_atac_preprocess step, all FASTQ files in .fastq.gz format are being decompressed into a new location, which consumes a significant amount of disk space. However, since Chromap supports gzipped input, it would be more efficient to retain the FASTQ files in their compressed format.

Could we implement a way to process fastq.gz files directly without the need for decompression? This adjustment would greatly optimize storage requirements.