[C++][FlightRPC] Inconsistent use of int, int32_t, uint32_t for SqlInfo enum values

[asfimport]

These should all be uint32_t, always. Not a big deal in practice at least.

Reporter: David Li / @lidavidm

_{Note: This issue was originally created as ARROW-17558. Please see the migration documentation for further details.}

[asfimport]

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