Add automatic API documentation generation

[melissawm]

Description

Supersedes #2049

Re-does the previous PR with additional fixes for docstring formatting. Some submodules had to be excluded from the build due to import errors; they may be added in the future once these errors are resolved.

Tests

Documentation builds correctly locally.

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.