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