1) Instead of making dbrm calls to writeVBEntry() per block,
we make these calls per batch. This can have non-trivial
reductions in the overhead of these calls if the batch size
is large.
2) In dmlproc, do not deserialize the whole insertpackage, which
consists of the complete record set per column, which would be
wasteful as we only need some metadata fields from insertpackage
here. This is only done for batch inserts at the moment, this
should also be applied to single inserts.