Change branching logic to enable caching again + rename vcf2mat to vcf2counts

[famosab]

Previously a branching mutated the meta maps which led to caching being disabled (when runnign with -resume). This PR fixes that and renames one module to match the script name.

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the pipeline conventions in the contribution docs
• Make sure your code lints (nf-core pipelines lint).
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• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

[d4straub]

I dont understand why that PR adds another process.

[famosab]

I dont understand why that PR adds another process.

I somehow was not able to create the files without ruining the caching (eg -resume did not recover cached files for everthing after the creation of these "samplefiles").

[d4straub]

LGTM!