revset: drop optimization about reordering "or" set elements The reordering optimization is more important for "and" than "or", given the implementation details about "addset" and "filteredset" - reordering "or" may help "__contains__" test but not iteration, reordering "and" could help both. We are going to simplify the tree to remove ordering information. Removing "or" reordering optimization would make things simpler. This effectively reverts c63cb2d10d6d. It tracks back to the "orset" function added by the initial commit of revset (c9ce8ecd6). In the future, we might consider optimization at runtime (ex. do reordering and rewrites inside "orset"). Differential Revision: https://phab.mercurial-scm.org/D561