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ARROW-15418: [Go][Flight] Update gRPC version, hide impl details

Updating the version of gRPC used and re-generating the protobuf files. Shifting the generated files to an internal directory and then using aliases to better control the names and what is exported so that future updates can be done without being breaking like this one is. This will go out with v8 and thus is okay to be a breaking change since it will be a major version change (and will be noted in the release notes).

It also smooths out the interface for Flight a bit as a result of the gRPC updates, making it easier and more obvious when creating flight servers and the corresponding auth handling.

Closes #12233 from zeroshade/update-grpc-flight-go

Lead-authored-by: Matthew Topol <mtopol@factset.com>
Co-authored-by: Matthew Topol <zotthewizard@gmail.com>
Signed-off-by: Matthew Topol <mtopol@factset.com>