The `ParseParams` Tool interface is only passing the tool's parameter
into a generic `parameters.ParseParams()` helper. Instead of keeping it
as a tool interface, we add a `GetParameters()` method
(https://github.com/googleapis/genai-toolbox/pull/2374) to the tool
interface and call it directly from the API handlers. This way we keep
the parameter parsing logic independent from the tools.
2d5d33388c