feat: add stub blocks for QC & filtering modules (#4570)

[HReed1]

Adds deterministic stub: blocks and corresponding -stub nf-test cases for QC & filtering modules, as part of the ongoing effort to resolve #4570. Split from the original monolithic #11323 per reviewer feedback.

Each stub generates placeholder output files matching the module's output channel declarations:

• Plain-text outputs use touch
• Compressed (.gz) outputs use echo | gzip >
• versions.yml blocks are copied 1:1 from the script block

Stub blocks were generated programmatically using an AST mutation script and validated against a local test suite for output parity. For full documentation on the tooling, conventions, and methodology used, see the Nextflow contribution docs.

Modules affected (5)

• fastqscan
• filtlong
• prinseqplusplus
• pycoqc
• rasusa

Tests

All modules include -stub nf-test cases with assertAll() + snapshot(process.out).match(). Snapshots generated locally via nf-test --update-snapshot.

PR checklist

Contributes to #4570. Split from #11323.

• This comment contains a description of changes (with reason).
• Stub tests added for all modules.
• Follows the module conventions in the contribution docs.
• Remove all TODO statements.
• Follow the naming conventions.

[HReed1]

@nf-core-bot fix linting

[HReed1]

Closing legacy batched PR in favor of atomic 1-PR-per-module approach with topic channel migration, as requested by reviewers.