bam_split_by_region

The input channel of this subworkflow containing:

• meta: Groovy Map containing sample information => doesn’t have a field called ‘genomic_region’
• bam: BAM/CRAM/SAM file
• bai: Index for BAM/CRAM/SAM file
• regions_file: A file containing the genomic regions used to separate the reads in the
  input bam. This should be a BED or TSV file containing either a single
  column of chromosome names, two columns (chromosome name and position),
  or three columns (chromosome name, start position, and end position).
  Structure: [ val(meta), path(bam), path(bai), path(regions_file) ]