obshashrange: fix computation of affected ranges The computation of impacted nodes and associated revs is fully reworked. In addition,we introduce multiple new tests covering cases that were previous wrongly handled.

obshashrange: add more validation output to tests We are about to update the logic and add more tests.

obshashrange: correctly detect changeset directly affected by prune Before this changesets, parent of standard obsmarkers were wrongly considered affected and pruned changeset were wrongly not considered affected.

obshashrange: do not search for affected ranges above the highest we have It is a fast way to know we don't have an affected range for an affected revision.