docs: use pydoc-markdown to generate API reference

[masci]

Instead of building the reference with mkdocs, we use pydoc-markdown to generate a markdown file from the docstrings in the sources. mkdocs will then treat this markdown file as any other documentation page.

Why?

• This way we can version the generated API docs
• The new documentation website will benefit from getting a markdown file ready to be rendered

Implications:

• Cross-references have a different format in pydoc-markdown so I had to change the docstrings
• The workflow section under the "API Reference" in the soon-to-be old documentation website has been removed
• Right now the generated markdown file is checked in, to be decided if it's better for the new docs website to generate it on-the-fly

[coveralls]

Pull Request Test Coverage Report for Build 17407236917

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.17%

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Totals
Change from base Build 17331658432:	0.0%
Covered Lines:	1155
Relevant Lines:	1201

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💛 - Coveralls

[logan-markewich]

@masci ooc, did we do any filtering on the exposed classes? Are there classes/functions that we don't want to expose?

[masci]

We're filtering out undocumented classes/functions and private classes/functions. _Resource is an exception because a public member depends on it (we might want to rename it).

[masci]

Discussed offline, the new developer portal will be able to support the existing mkdocs-generated api reference, closing.