perf: allow to clear the obsstore in 'perfvolatilesets' Loading the obsstore can become a large part of the time necessary to compute the important volatile set. We add a flag purging all known obsstore related data. For example, computing the 'bumped' set currently requires reading the full obsstore, so timing greatly differ with or without that flag: Without: ! bumped ! wall 0.005047 comb 0.000000 user 0.000000 sys 0.000000 (best of 446) With: ! bumped ! wall 0.512367 comb 0.510000 user 0.480000 sys 0.030000 (best of 15)