[C++][Python][FlightRPC] Use StopToken to enable interrupting long Flight operations

[asfimport]

For example, calling do_get().read_all() can't be interrupted with Ctrl+C in Python.

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

PRs and other links:

• GitHub Pull Request #10318

_{Note: This issue was originally created as ARROW-12050. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 10318
#10318