Remove DataFusionError::into_arrow_external_error in favor of From conversion

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
The way to convert DataFusionError into an ArrowError is confusing for Rust programmers coming to the DataFusion codebase and makes our codebase a bit of a mess

DataFusionError::into_arrow_external_error

They typically expect a impl From<..> conversion trait

Describe the solution you'd like
Once #1642 is complete, we can remove DataFusionError::into_arrow_external_error and just use ?

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.