Store sample ancestry in sample refs. Group samples by sample type in matrix

[gavrielm]

Description

When a dataset has sample ancestry (ds.cohort.termdb.hasSampleAncestry=true), the sample ancestry will get stored in the sample refs. In matrix, the sample ancestry can then be accessed in the sample refs to group samples by root sample type.

Can test by launching an NB2012 matrix of a sample-level term. The samples will be grouped by patient by default.

Checklist

Check each task that has been performed or verified to be not applicable.

• Tests: Added and/or passed unit and integration tests, or N/A
• Todos: Commented or documented, or N/A
• Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A
• Rust: Checked to see whether Rust needs to be re-compiled because of this PR, or N/A