fix: update iox.sql to detect midstream errors

[wolffcm]

This updates the IOx client abstraction to produce a reader that has an Err() method (which the Flight implementation does), and updates the implementation of iox.sql to check it for errors.

Prior to this change, midstream errors would be ignored and the result would be truncated.

These changes address a defect found in the cloud product, with tests added to the PR there.

BREAKING CHANGE: breaks the Go API for the IOx client dependency.

Checklist

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