Resolves #1936: Reduce unnecessary clears of legacy version space #1937
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This reduces the number of unnecessary clears issued during check version by being more precise about when the legacy version subspace is cleared. It will only clear the range now if (1) the store is not new and (2) the store header suggests that any versions in the old store would have been stored in the old space. It introduces a test that validates that the version is cleared if versions were stored in that old subspace and the meta-data is changed to so that versions are no longer stores. That test valdiates that there are fewer range clears now if the range doesn't have to be cleared, but other than that assert, the test asserts pass both before and after the main code changes.
This resolves #1936.