Move physical plan serde from Ballista to DataFusion #3949
Description
Is your feature request related to a problem or challenge? Please describe what you are trying to do.
datafusion-proto supports logical plan serde, but physical plan serde is in Ballista.
Describe the solution you'd like
Move most physical plan serde code to DataFusion. Ballista will still need serde code for its own physical operators that are not part of DataFusion.
Describe alternatives you've considered
None
Additional context
See discussion at #3907 (comment)