Add metamap for input/output in stringtie/merge

[Odulhin]

Summary

• Add a metamap for input, output instead of the previous harcoded ones
• Modify related subworkflow : bam_stringtie_merge
• Update snapshots

Closes #8686

[famosab]

Thank you for your contribution to nf-core! We really appreciate it. I added a few comments to your PR. Good work updating this module to adhere more to the nf-core guidelines

[famosab]

Can we put all these inputs into one tuple? That will make sure you're sure that EVERY time everything comes together in the right combination.

[Odulhin]

I tried but I had issues to pass tests afterwards.

Instead I put the annotation_gtf inside a metamap which was easier and required less code modifications because in the related subworkflows it was already in this form only the metadata was discarded when calling the module.

[famosab]

You can run

nextflow lint -format -sort-declarations -spaces 4 -harshil-alignment

on this file to clean this up nicely.

[Odulhin]

Thanks !