singularity: update configs to use docker hub and specified cacheDir

src/nf_modules/samtools/sort_bams.config

src/nf_modules/samtools/split_bams.config

src/nf_modules/sratoolkit/fastqdump.config

src/nf_modules/subread/subread.config

src/nf_modules/urqt/trimming_paired.config

src/nf_modules/urqt/trimming_single.config