Add support for COPY TO in tablesync for partitioned tables.

Hi all,

After patch [1] was committed, the COPY TO command is now supported
for partitioned tables. This change updates the tablesync logic to use
COPY TO for partitioned tables as well. This change will only be
invoked when the publication is configured with
publish_via_partition_root = true;
otherwise, partitioned tables will continue to be published using
their underlying partitions by default and publishing using partitions
already use COPY TO.

[1] - https://github.com/postgres/postgres/commit/4bea91f21f61d01bd40a4191a4a8c82d0959fffe

regards,
Ajin Cherian
Fujitsu Australia