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GH-37726: [Swift][FlightSQL] Update behavior to be similar to existing impls (#37764)

Swift Flight implementation behavior didn't match existing flight implementations.  The updates in this PR have been tested against python/examples/flight/server.py except for getSchemaTest and doExchangeTest which are not implemented in server.py.  I will follow up this PR with a cleanup refactoring PR.

This difference in behavior was found due to issue #37726.  
* Closes: #37726

Authored-by: Alva Bandy <abandy@live.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>