refactor validators to remove duplicate files

[gvwilson]

This PR replaces #5173 by rebasing @bmaranville's changes on top of main. Please see #5173 for detailed notes about the motivation and changes. The important changes are in:

• codegen/init.py

• codegen/datatypes.py

• codegen/validators.py

• doc/python/marker-style.md

• plotly/_subplots.py

• plotly/basedatatypes.py

• plotly/figure_factory/_annotated_heatmap.py

• plotly/io/_templates.py

• plotly/validator_cache.py

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the codegen files and not generated files.

• I have added tests (if submitting a new feature or correcting a bug) or
  modified existing tests.

• For a new feature, I have added documentation examples in an existing or
  new tutorial notebook (please see the doc checklist as well).

• I have added a CHANGELOG entry if fixing/changing/adding anything substantial.

• For a new feature or a change in behaviour, I have updated the relevant docstrings in the code to describe the feature or behaviour (please see the doc checklist as well).

[gvwilson]

@alexcjohnson if you have time to look this over we'd be grateful for your feedback

[emilykl]

revert this line -- needs to remain the same as what's in pyproject.toml

Suggested change

	BLACK_TARGET_VERSIONS = "py39 py310 py311 py312"
	BLACK_TARGET_VERSIONS = "py38 py39 py310 py311 py312"

[emilykl]

🔪

[bmaranville]

Does the knife symbol mean you want to remove this code?

[emilykl]

Ha, yes, sorry @bmaranville -- by 🔪 I mean delete this line 😄 (the commented-out one)

[emilykl]

🔪

[emilykl]

@bmaranville The file plotly/validators/_validators.json needs to be flagged in the pyproject.toml so that it's included in the built package.

I think the correct way is to add it to the list under [tool.setuptools.package-data].

[emilykl]

Thanks for the PR @bmaranville ! Other than my comments above, looks good to me. The tests are passing and validation seems to be working as usual in the examples I've tried. (@alexcjohnson I'm curious whether you can see any possible pitfalls or edge cases here -- happy to do more testing of specific cases if you have concerns.)

[alexcjohnson]

@bmaranville nice work, this is a clever solution! Two small thoughts about it:

• We should be able to reduce the whitespace significantly, to make the file smaller. Could even collapse it to a single line, I'm not sure there's much value keeping it human-readable, but maybe @emilykl has opinions about this. If we really want to optimize file size we could also change its structure a bit - like if every entry is a dict {params, superclass} this could be converted to a length-2 list. But the whitespace is the biggest piece of this.
• json.load is pretty fast, ~41ms on my computer. But it's even faster if we just make this a Python file. In my quick test I just added:

true=True
false=False
null=None
v = 

to the beginning of the file to convert the JSON to Python, and then from validators._validators import v took only ~25ms. (If we do this for real we should be able to tweak the json.dump to output Python in the first place so we don't need to alias true, false, and null)

@emilykl the only thing I'm not 100% confident of is whether this has any type checking implications. I don't think so, I think the only type checking that matters is on graph_objs, not validators, but we do currently have if TYPE_CHECKING blocks in all the __init__.py files in validators, ensuring that type checkers will load them all. If you haven't done so already it's probably worth playing around on this branch a bit to convince ourselves that we don't lose anything important with this.