Allow sorting inputs to SVDB

[fellen31]

This PR adds functionality for sorting the input files to SVDB. This allows the output to be snapshot when this module is included in a subworkflow, since the sample order in the output files will be fixed. The priority tags are sorted together with the VCFs, so the priority order is unchanged.

It also adds a check to make sure there are as many priority tags as input VCFs.

Tests should cover all usages.

PR checklist

Closes #XXX

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[ramprasadn]

LGTM! Can you just add a note saying that the order of the vcf files should correspond to the values in the priority channel? I should have done that when I first added the module, but better late than never 😄

[fellen31]

Thanks! I think it was already in there, but I clarified the meta.