458 make public improvements

[hiker]

Addresses #458:

1. Leave comments in the code (to support UM-style "depends on" comments)
2. Add example code of how to leave some definitions unchanged, used to leave "DrHook variables" like ModuleName private (these can cause compilation failures if wildcard imports are used, because a module then ends up with two conflicting definitions). The code does not change anything atm (i.e. the list of names to ignore is empty), so no change unless a user changes this definition. We do this in our LFRic-build environment for example.
3. I also added more comments to the 'ignore_comments` docstring. Admittedly, it was actually clear and I was overthinking things, but I guess making this explicit can't hurt.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.05%. Comparing base (3bc75fe) to head (4b64bea).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #459      +/-   ##
==========================================
- Coverage   92.14%   92.05%   -0.09%     
==========================================
  Files          86       86              
  Lines       13834    13738      -96     
==========================================
- Hits        12747    12647     -100     
- Misses       1087     1091       +4     

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[hiker]

The CI failure is not caused by this PR:

Run actions/setup-python@v4
Installed versions
  Version 3.7 was not found in the local cache
  Error: The version '3.7' with architecture 'x64' was not found for Ubuntu 24.04.
  The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json

I could manually trigger the 3.8 run, but 3.11 keeps on getting cancelled

[arporter]

We had this problem with the PSyclone repo too - we had to downgrade the version of Ubuntu used for the runner in order to retain 3.7 support.