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GH-34472: [Go][FlightRPC] Drain result of DoAction in Flight SQL client (#34473)

### Rationale for this change

Unless we drain the result of DoAction, we can't be sure that the RPC actually completed.

### What changes are included in this PR?

Always drain the result of DoAction.

### Are these changes tested?

A new test was added and existing tests were modified.

### Are there any user-facing changes?

This fixes potential nondeterministic behavior that users may have previously observed.
* Closes: #34472

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: David Li <li.davidm96@gmail.com>