[C++][FlightSQL] Add caching of FlightClients to ODBC

[alinaliBQ]

Describe the enhancement requested

This is a mirror of the JDBC issue apache/arrow-java#157

AC:

• When FlightInfo reports a list of endpoints, the driver internally creates a FlightClient for each endpoint that reports a Location. These clients can benefit from being cached/pooled since a server will likely re-use endpoints for subsequent queries. This should likely be a configuration option.

The driver should also check if the Location at an endpoint is the same as the original location used when creating FlightStreamChunkBuffer and avoid creating a new FlightClient in this case.

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Parent issue: #30622

Component(s)

FlightRPC, C++