Refactors the test codebase to use tools instead of functions.
- Rename FunctionCallback to FunctionToolCallback
- Rename FunctionCallingOptions to ToolCallingChatOptions
- Update API methods from functions() to tools()
- Deprecate function-related methods in favor of tool alternatives
- Refactor MethodToolCallback implementation with improved builder pattern
- Update all tests to use new tool-based APIs
- Add funcs to tools migration guide
Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>
