Auto merge of #97862 - SparrowLii:superset, r=lcnr

optimize `superset` method of `IntervalSet`

Given that intervals in the `IntervalSet` are sorted and strictly separated( it means the `end` of the previous interval will not be equal to the `start` of the next interval), we can reduce the complexity of the `superset` method from O(NMlogN) to O(2N) (N is the number of intervals and M is the length of each interval)

Author: bors