ViewBuilder can miss data due to sstable generation filter

The view builder for one MV is restarted when other MVs are added on the same keyspace. There is an issue if compactions are running between these restarts that can cause the view builder to skip data, since the builder tracks the max sstable generation to filter by when it starts back up.

I don't see a need for this generation tracking across restarts, it only needs to be tracked during a builders life (to avoid adding in newly compacted data).