Add clustering test tsv

[dbaku42]

Add test dataset for pcaclustering

This PR adds a new minimal dataset (test.tsv) for the pcaclustering functionality within the clustering test suite.

The dataset is added under:

data/genomics/homo_sapiens/popgen/clustering/

and is intended to support reproducible unit testing of PCA-based clustering workflows.

This addition is related to:
nf-core/modules#11372

Purpose

• Enable robust testing of pcaclustering logic in nf-core modules
• Provide a minimal, reproducible input dataset for CI and nf-test execution
• Ensure compatibility with existing clustering test assets (test_features.tsv, test_clusters.csv, etc.)

Dataset generation

The test.tsv file was generated from test.eigenvec using the following awk command:

awk 'NR==1 {
  sub(/^#/, "");
  $1 = "";
  sub(/^\t/, "");
  sub(/^IID\t/, "sample_id\t");
  print;
  next
}
{
  $1 = "";
  sub(/^\t/, "");
  print
}' OFS='\t' test.eigenvec > test.tsv