hidden: unify the static and dynamic blocker logic We no longer have cache and they both work the same way. Unifying the logic simplify the code and reduce the amount of set copies.

hidden: drop the hidden cache logic The improvement in time complexitty and the speed-up in computation is large enough that the has little use now. Its update time can even gets in the way. So we drop it. This will allow us to unify the static/dynamic blockers logic in the next changeset.

hidden: simplify the computation of consistency blocker For a couple of years, we now have precomputed set for all mutable phases. We can use this set restrict our search and quickly detect non-hideable children of hideable changesets. This speeds up the hidden computation. See docstring of the new function for details. This new version reuses the '_domainancestors' function to keep the computation of revealed changeset in O(len(visible)) Below are perfvolatilesets timing from two Mozilla repositories with different contents. hidden cache is disabled while obtaining them. 1) Mozilla repository with: * 400667 changesets * 35 hidden changesets (first rev-268334) * 288 visible drafts * 1 unstable changeset Before: ! visible ! wall 0.001744 comb 0.000000 user 0.000000 sys 0.000000 (best of 1563) After: ! visible ! wall 0.000742 comb 0.000000 user 0.000000 sys 0.000000 (best of 3755) The timing above include the computation of obsolete changeset: ! obsolete ! wall 0.000396 comb 0.000000 user 0.000000 sys 0.000000 (best of 6816) So adjusted time give 1.3ms before versus 0.3ms after. A 4x speedup. 2) Mozilla repository with: * 405645 changesets * 4312 hidden changesets (first rev-326004) * 264 visible drafts * 1 unstable changeset Before: ! visible ! wall 0.025476 comb 0.030000 user 0.030000 sys 0.000000 (best of 111) After ! visible ! wall 0.007703 comb 0.010000 user 0.010000 sys 0.000000 (best of 358) The timing above include the computation of obsolete changeset: ! obsolete ! wall 0.006408 comb 0.010000 user 0.010000 sys 0.000000 (best of 404) So adjusted time give 19ms before versus 1.3ms after. A 17x speedup.