Adding feature tracking operator

[Adam Gainford (A-Gainford)]

Adding feature-tracking via the Simple-Track repo (https://github.com/ParaChute-UK/simple-track), which is included as a new dependency. The feature.track operator is used to call Simple-Track, which returns three cubes per timestep: "feature_id", "feature_lifetime" and "feature_init". These can be filtered to select them for plotting with existing routines. Other data which is not currently used by CSET can be saved for further analysis. The new "feature" operator set will also be used to implement cell stats using Simple-Track with the tracking capabilities disabled (though the "feature" name may want to be changed).

Contribution checklist

Aim to have all relevant checks ticked off before merging. See the developer's guide for more detail.

• Documentation has been updated to reflect change.
• New code has tests, and affected old tests have been updated.
• All tests and CI checks pass.
• Ensured the pull request title is descriptive.
• Ensure rose-suite.conf.example has been updated if new diagnostic added.
• Conda lock files have been updated if dependencies have changed.
• Attributed any Generative AI, such as GitHub Copilot, used in this PR.
• Marked the PR as ready to review.