[C++][FlightRPC] Support alternative transports in the Flight benchmark

[asfimport]

A follow-up to ARROW-15282.

Reporter: David Li / @lidavidm
Assignee: David Li / @lidavidm

Related issues:

• [C++][FlightRPC] Support non-grpc data planes (relates to)

PRs and other links:

• GitHub Pull Request #12524

_{Note: This issue was originally created as ARROW-15788. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 12524
#12524