Update version and fix samples for 0.8.5 release

[MarkDaoust]

1. Update version number for 0.8.5 release
2. Set "Development Status :: 7 - Inactive"
3. Next releases will pickup the README as the main page on PyPi, so this will show the current readme's "[DEPRECATED]".
4. Fix broken samples (all samples pass now).
5. Fix empty GEMINI_API_KEY="" shadowing "GOOGLE_API_KEY".
6. Fix tests broken by pydantic 2.11
7. Remove duplicate/orphaned code broken by pydantic2.11 (responder.py)
8. Sync readme to match Add Support Plan for the repository and deprecation timeline. deprecated-generative-ai-js#462

[Annhiluc]

Add reason that google/generativeai/responder.py is deleted to the PR?

[MarkDaoust]

Add reason that google/generativeai/responder.py is deleted to the PR?

Added to the main description.
Mainly: this was the start of development for a feature that was never completed (forked from content_types.py). It should have been done on a feature branch instead of in main. While the file name doesn't start with an underscore, it's never been mentioned externally.

Anyway, people could be importing it. So maybe this is a bit much to put in a bug fix release. I've copied in the fixed code from content_types.py, minimal update, all the tests pass now.

Done.