INTPYTHON-482 Add API docs

[blink1073]

I made the following tweaks to create_api_rst.py:

• Used api_docs.rst as the root doc to avoid overshadowing langchain-mongodb/index.py
• Fixed handling of the namespace package for langgraph
• Handle __all__ if present
• Removed some custom title handling for other partner packages

I made the following tweaks to conf.py:

• Removed custom examples directive
• Updated metadata for this repo

[blink1073]

Langgraph failure is unrelated: https://jira.mongodb.org/browse/INTPYTHON-488

[caseyclements]

These docs look great.

When I build them, langgraph.checkpoint.mongodb.MongoDBSaver is not showing up. AsyncMongoDBSaver does, but not the main one.

[blink1073]

When I build them, langgraph.checkpoint.mongodb.MongoDBSaver is not showing up. AsyncMongoDBSaver does, but not the main one.

I had to do some restructuring of files to get it to show up. __init__ files are ignored.

[caseyclements]

lgtm