Migrate Flight and FlightSql Proto Gen #89
Description
Flight and FlightSql definitions are still in apache/arrow.
The go_package name will need to be updated to match this repo, and the actual codegen will need to be ported as well. We will no longer be able to use a direct reference to the .proto files, so we may need to use git submodules or a tool like buf in order to build the needed files.