Add REGENIE chunked step 1 modules

[lyh970817]

REGENIE is a C++ program for whole-genome regression modelling of large GWAS cohorts. This PR adds a chunked Step 1 module family that exposes REGENIE's native level-0 parallelization workflow:

• regenie/splitl0 creates the level-0 split master file and per-job SNP lists.
• regenie/runl0 runs one level-0 job from the split master file.
• regenie/runl1 gathers the level-0 outputs and finishes Step 1, producing the standard prediction list and LOCO files consumed by regenie/step2.

This PR depends on the base regenie/step1 module in #11008.

PR checklist

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• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • For modules:
    • nf-core modules test regenie/splitl0 --profile docker
    • nf-core modules test regenie/runl0 --profile docker
    • nf-core modules test regenie/runl1 --profile docker
    • nf-core modules test regenie/splitl0 --profile singularity
    • nf-core modules test regenie/runl0 --profile singularity
    • nf-core modules test regenie/runl1 --profile singularity
    • nf-core modules test regenie/splitl0 --profile conda
    • nf-core modules test regenie/runl0 --profile conda
    • nf-core modules test regenie/runl1 --profile conda