Do NOT convert intermediate/source errors to strings.

[crepererum]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Now that DF emits ResourceExhausted errors for out-of-memory situations, it would be nice if the API user could somehow detect this situation (e.g. to convert this to a suitable HTTP status code).

Describe the solution you'd like
There are a few places where we convert errors to strings, mostly to wrap them into DataFusionError::Execution(...). However DF (and Arrow) have ways to wrap arbitrary error types (external error). To send errors to multiple receivers, they can easily be wrapped into Arcs (Arc forwards std::error::Error).

Describe alternatives you've considered
Perform string "parsing" on the top-level err.to_string(). This is pretty bad code smell.

Additional context
See #3940 for an application.

[crepererum]

I'm working on this.