feat: make qualify faster by owly resetting scope when needed

[tobymao]

No description provided.

[georgesittas]

What about the column.replace calls in L331 & L341?

[tobymao]

it didn't fail any tests

[georgesittas]

I suggest being conservative in this case; the refactor feels inconsistent otherwise and we won't be able to easily reason about what went wrong in the future, if it happens.

[tobymao]

i don't think it's necessary because the names don't change, i don't think we should just add code for no reason

[georgesittas]

My concern was about the references changing, not the names. Also, L341 replaces a column with a number, so its name does change in that case.

In any case, the reason for my suggestion was that we'd be more faithful to the previous implementation with minimal overhead, thus minimizing the risk & we don't need to reason about how other parts are affected. The benefit of this PR is that we don't always call scope.clear_cache(), but only if necessary– that'd still be true.

Feel free to disregard if you're good with the change as-is.