feat: Context+Settings APIs

[tmathern]

Changes in this pull request

Main changes are in src/c2pa/c2pa.py.

• Add Context and Settings APIs (+bump of c2pa-rs)
• Add tests to verify feature parity of context APIs with existing APIs
• Update examples, add "no_thumbnails.py" example showing how to use settings to turn off thumbnails
• Update usage docs, and add ManagedResource class docs (more docs are in docs: Document Context+Settings API, Intents, Working Stores #235)
• Remove unused toml settings file (Python only uses JSON settings)
• Fix typos and bugs caused by typos in src/c2pa/lib.py
• Prune some tests that tested features covered by other tests
• Removed bindings for unused APIs (the "old" embeddable ones, which where not bound in Python), added missing bindings for fragments

Checklist

• This PR represents a single feature, fix, or change (new API: context with settings).
• All applicable changes have been documented.
• Any TO DO items (or similar) have been entered as GitHub issues and the link to that issue has been included in a comment.