Fixes#7119Fixes#7120
If preimage select came up empty - i.e. the row did not exist, either
due to never been created, or once delete, we should not bother creating
a log preimage row for it. Esp. since it makes it harder to interpret the
cdc log.
If an operation in a cdc batch did a row delete (ranged, ck, etc), do
not generate postimage data, since the row does no longer exist.
Note that we differentiate deleting all (non-pk/ck) columns from actual
row delete.
e50911e5b0