[substrait] more abstract SubstraitConsumer API

[vbarua]

Is your feature request related to a problem or challenge?

The code in #13803 adds a SubstraitConsumer trait that explicitly includes the following methods

    fn get_extensions(&self) -> &Extensions;
    fn get_function_registry(&self) -> &impl FunctionRegistry;

these methods are used by implementors to retrieve structs, which they can then use to resolve and map functions from Substrait into DataFusion.

IMO, these structs are internal implementations detail and should be replace by dedicated methods that do not leak these details.

Describe the solution you'd like

Identify / devise a series of API methods for the SubstraitConsumer that can be used to replace the calls to get_extensions and get_function_registry.

This may require rethinking how functions are mapped from Substrait to DataFusion

Describe alternatives you've considered

No response

Additional context

No response