Extension mechanism for SessionConfig #2939

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
As a DataFusion user (concrete: the IOx team) I would like to be able to bind Any object to the SessionConfig so all traits that receive SessionState (e.g. TableProvider::scan) to receive application-specific objects, e.g. for tracing or caching.

Describe the solution you'd like
Attach some Arc<dyn Any> to SessionConfig.

Describe alternatives you've considered

• Using the SessionState instead. I find that application-specific "stuff" might be better attached to the config, but I don't have a strong opinion on that.
• Use the existing ConfigOptions. The problem is that these options only allow ScalarValues to be attached, which is not powerful enough to hold arbitrary objects.

Additional context
None.