Fix slice ordering and add new test data

[d33bs]

Description

This PR fixes an issue where individual z-slice files referenced to create a composite are not sorted properly by their z-slice filename ordering specification.

Changes are made to the function which reads file-based data and also to the test data to help demonstrate that all z-slices are in order. We now simulate cell-like sphere images and labels within the test data.

Along the journey here I also found that Napari was crashing frequently during tests. I was able to resolve some of these crashes by using the show parameter with "headless" (non-Napari window appearing) mode for views.

Many thanks to @MattsonCam who helped uncover this bug.

What kind of change(s) are included?

• Documentation (changes docs or other related content)
• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (these changes would cause existing functionality to not work as expected).

Checklist

Please ensure that all boxes are checked before indicating that this pull request is ready for review.

• I have read and followed the CONTRIBUTING.md guidelines.
• I have searched for existing content to ensure this is not a duplicate.
• I have performed a self-review of these additions (including spelling, grammar, and related).
• These changes pass all pre-commit checks.
• I have added comments to my code to help provide understanding
• I have added a test which covers the code changes found within this PR
• I have deleted all non-relevant text in this pull request template.

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[MattsonCam]

LGTM @d33bs, good job! I didn't check the z-slice images, but I want to include an example in our GFF discord channel. Can you DM me on discord to lmk how I can apply these changes? I anticipate it will just be updating the version of nViz.

[d33bs]

Thanks @MattsonCam for the review! I'm going to merge this in after making some changes based on your comments. Afterwards, I'll plan to deploy a new release for nviz so it may be used readily with these fixes via uvx without special handling. Like we talked about, there is likely a way to reference remote packages through uvx, but if not, we should be able to use the PyPI package.

[d33bs]

Hi @MattsonCam - this fix is now deployed within v0.0.5 of nviz (and should be available to uvx).