asserts.set_equals uses old_sets.bzl

The behavior of `asserts.set_equals` is confusing (it uses old_sets instead of sets) and should be updated.

Start by locating asserts.set_equals in old_sets.bzl and inspect how it currently refers to old_sets versus sets. Trace the related sets definitions or usages in the repository to confirm the intended implementation, then verify that set equality uses the current sets behavior without changing the assertion API.

Written by the indexing model from the issue text.