`<algorithm>`: Avoid extra range traversals from `ranges::next(iterator, sentinel)`

ranges::advance(iterator, sentinel) and consequently ranges::next(iterator, sentinel) are O(1) when sentinel can be assigned to iterator, or when iterator's type models random_access_iterator and sentinel and iterator's types together model sized_sentinel_for. Otherwise, these overloads of ranges::advance and ranges::next are O(N).

There are occurrences these expressions in the Ranges code that are fine/efficient when O(1), but not great when O(N). Audit and investigate if some of these could be improved by replacing an approach that needs the final iterator with one that is purely forward.

(<algorithm> is the primary offender, but this also applies to Ranges code in <xutility>, <memory>, and possibly <xmemory>.)

Search the Ranges implementations in first, then audit corresponding uses in , , and possibly . Review each ranges::advance(iterator, sentinel) and ranges::next(iterator, sentinel) occurrence for avoidable O(N) traversal. Done means improving applicable cases with a forward-only approach while preserving existing behavior and validating the affected library tests.