fix: use selection vector to ensure ids are ordered

[lokax]

static idx_t SortSelectionVector(SelectionVector &sel, idx_t count, row_t *ids)
SortSelectionVector does not actually sort ids, but ensures that ids are ordered through SelectionVector

The algorithm in CheckForConflicts needs to traverse the ids in order, which requires a SelectionVector to guarantee.

[Mytherin]

Thanks for the PR!

Looks good and seems correct, but do you have an example/could you add a test that triggers the bug in the original code and works with this change?

[Mytherin]

Thanks!