Vacuum Completely Deleted Row Groups #7794
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Partially implements #109
This PR implements support for vacuuming fully deleted row groups during the checkpoint process. For row groups that have no valid tuples anymore - we can strip them out entirely during a checkpoint and re-use the space for future operations. There is one limitation which is that we do not vacuum in the presence of indexes yet. Vacuuming in the presence of indexes requires rewriting the row identifiers stored in the index - so for now we simply skip the vacuuming process in this scenario.
In a future PR we also plan to merge row groups that are partially empty due to deletions, so that we can also clean up partial deletions past a certain threshold.