Make from_proto_binary_op public

[askoa]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
The function from_proto_binary_op converts string to Operator. This function is required by downstream arrow-ballista and currently duplicated in that project. So whenever a new operator is included, the function from_proto_binary_op should be updated in both arrow-datafusion and arrow-ballista project. This is redundant.

https://github.com/apache/arrow-datafusion/blob/5f029cc73755b6800217e370ebe0a7b5e8a6a224/datafusion/proto/src/from_proto.rs#L1518-L1521

Describe the solution you'd like
The solution is to make the function from_proto_binary_op public in arrow-datafusion project and use it in arrow-ballista project.

Additional context
See comments in the below issue for more details.

apache/datafusion-ballista#201