have rootFinalizerIter implement sql.MutableRowIter

[jycor]

We've moved rules out of analyzer into FinalizeIters so the applyRowUpdateAccumulator is applied afterwards.
However, this seems to be a special sql.RowIter, so we need to expose the child iterators through the sql.CustomRowIter interface to apply that rule

[github-actions]

	Main	PR
Total	42090	42090
Successful	12877	12877
Failures	29213	29213
Partial Successes1	4893	4893

	Main	PR
Successful	30.5940%	30.5940%
Failures	69.4060%	69.4060%

Footnotes

1. These are tests that we're marking as Successful, however they do not match the expected output in some way. This is due to small differences, such as different wording on the error messages, or the column names being incorrect while the data itself is correct. ↩

[max-hoffman]

Reading through the implementations again, it might be better if iterators destined for update accumulator wrapping exposed an interface, if only to make the code less brittle.

[max-hoffman]

LGTM, couple comments on GMS side