Change java package names in protobuf files

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
We are using non-standard Java package names org.datafusioncompute and org.ballistacompute in the .proto files. I believe it would be better practice to use package names starting with org.apache.arrow, such as org.apache.arrow.datafusion and org.apache.arrow.ballista.

Describe the solution you'd like
As described.

Describe alternatives you've considered
None

Additional context
None