[Bug] Copy/graft should not revert but instead do this

[lutter]

Bug report

After all the data for a graft has been copied, we revert the destination to the graft block

For large subgraphs, that will be very slow. Instead of reverting, we should unclamp entity versions while we copy, i.e. instead of blindly copying the block_range from the source, we should insert something like

case when upper(block_range) <= $graft_block then block_range
         else int4range(lower(block_range), null) end as block_range