feat: fix biosample study validation

[Tobi1kenobi]

✨ Context

Fixes a bug in the study validation where checking studies for biosample index would drop all GWAS studies. Also implements additional testing to catch this scenario in the future.

🛠 What does this PR implement

Changed the logic of the biosample_index study validation slightly to match the gene_index study validation a bit closer. Also modified the TestGeneValidation suite to be more abstract and inclusive i.e. be applicable to any study validation that is only for QTLs.

🙈 Missing

One function is duplicated instead of abstracted as the amount of code written was similar so I thought perhaps better to keep simple.

🚦 Before submitting

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[DSuveges]

This PR updates the biosample validation logic:

• A new column (biosampleId) is added to the studyIndex schema.
• Only non-gwas studies are validated for biosamples.
• The validation adds a new column biosampleId to the resulting dataset, indicating valid biosample identifiers.
• Tests were provided.