Replays generated logs into every store, compacts, replays the compaction into fresh stores, and requires the same answers — including the blob reference counts a compaction rebuilds from the order it writes entries in. A second test requires compacting twice to equal compacting once, and both assert the corpus reached each state worth compacting. Change-Id: I2195be00d0e6bec11202211be67741f94c0b9c4c