refactor: different pattern for structured annotations list and shapes union

[tlambert03]

This PR improves the implementation of StructuredAnnotations and ShapeUnion.

These have been difficult objects to capture in a way that feels natural in a python context, while remaining true to the semantics of the original OME schema.

In ome-types v0.4, these objects both became list-like objects that removed the individual sub-fields. That is, they looked a bit more like this:

class OME(BaseModel):
    structured_annotions: list[XMLAnnotation | FileAnnotation | ListAnnotation] = []

than this:

class StructuredAnnotations(BaseModel):
    xml_annotations: list[XMLAnnotation]
    file_annotations: list[FileAnnotation]
    list_annotations: list[ListAnnotation]

class OME(BaseModel):
    structured_annotions: StructuredAnnotations | None = None

However, that came a bit at the expense of "correctness", and it also made the casting to JSON schema a bit clunky as well (which was recently fixed in a somewhat hacky way in #235).

This PR moves back towards the second pattern: a type StructuredAnnotations that does indeed have individual fields, matching the original XSD more faithfully... but it adds methods to that object that implement most (but not all) of the MutableSequence interface. That is, you can still use append, extend, remove, __getitem__ (but not __setitem__) on the object itself.

It's a significant internal refactor, but hopefully shouldn't break any external use cases (and the third-party tests for aicsimageio, omero-cli-transfer, and paquo are all still working after this PR).

[codecov]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (af72da7) 86.33% compared to head (4f5718f) 86.75%.

Files	Patch %	Lines
src/ome_types/model/__init__.py	45.45%	6 Missing ⚠️
src/ome_types/_mixins/_collections.py	96.55%	2 Missing ⚠️
src/ome_autogen/_generator.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #237      +/-   ##
==========================================
+ Coverage   86.33%   86.75%   +0.41%     
==========================================
  Files          26       24       -2     
  Lines        1259     1200      -59     
==========================================
- Hits         1087     1041      -46     
+ Misses        172      159      -13     

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[codspeed-hq]

CodSpeed Performance Report

Merging #237 will improve performances by 25.59%

_{Comparing better-structured-annotations (4f5718f) with main (af72da7)}

Summary

⚡ 1 improvements
✅ 8 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	better-structured-annotations	Change
⚡	test_time_to_xml[large]	8 s	6.3 s	+25.59%

[joshmoore]

Wow! That looks like it was painful, @tlambert03. Thank you!

I'm not sure I will be able to test before disappearing for the holidays, but it's definitely on my list.