Add anatomical groups example

[user27182]

Overview

Add full example showing how to plot different anatomical groups from the whole_body_ct datasets. Preview image showing a plot of the cardiovascular system:

TODO

Dependencies:

• Merge extract_values filter from Add extract_values filter and update connectivity filter to use it #5963
• Merge updates to contour_labeled filter from Update contour_labeled filter #5968
• Upload color dict to pyvista/vtk-data repo mapping labels to colors for the whole_body_ct datasets

Update whole_body_ct datasets:

• Add color dict mapping to the user_dict for these datasets
• Add new kwargs to enable loading only part of the dataset, i.e. integrate the utility functions from the full example into the loading functions
  e.g. download_whole_body_ct(['heart']) to load only the heart label for this dataset.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.89%. Comparing base (4bc3487) to head (245f391).
Report is 4 commits behind head on main.

❗ Current head 245f391 differs from pull request most recent head 752986a. Consider uploading reports for the commit 752986a to get more accurate results

Additional details and impacted files

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