feat(util-genai): refactor and make API smaller and more user-friendly (#4391)

* Refactor public API on GenAI utils

* more lint

* review feedback

* update tests to use named params

* address some of the comments

* up

* fix failing checks and clean up imports

* lint

* lint

* fix lint

* replace @deprecated with docstring info to avoid warnings for users

* up

* common code for context manager