python3.sif: containerize tools

[espenhgn]

Fixes #302

Changes proposed in this pull request:

• adds plink2 binary, and dask, pyarrow, fastparquet to python3.sif build
• bumps version to 1.9.1 (new release)

Before submitting

• I've read and followed all steps in the Making a pull request
  section of the CONTRIBUTING docs.
• I've updated or added any relevant documentation and docstrings where appropriate in the codebase.
• If this PR fixes a bug, I've added a test that will fail without my fix.
• If this PR adds a new feature, I've added tests that sufficiently cover my new functionality.

[Copilot]

Pull Request Overview

This pull request updates the python3.sif container by adding plink2 and additional packages (dask, pyarrow, fastparquet) as well as updating the version to 1.9.1.

• Bumps the release version by setting the version suffix to an empty string
• Adds tests for the new plink2 binary and updates the package list in the tests
• Updates the CHANGELOG.md to reflect the new release and added features

Reviewed Changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated no comments.

File	Description
version/version.py	Updates the version suffix for the release version
tests/test_python3.py	Adds tests for the plink2 binary and updates package list for new dependencies
CHANGELOG.md	Documents the new release version and added packages to the container

Files not reviewed (2)

• docker/dockerfiles/python3/Dockerfile: Language not supported
• docker/scripts/apt_get_essential.sh: Language not supported