Enhance follow_primary.sh generation in pgpool_setup.

Enhance follow_primary.sh generation in pgpool_setup.

In the generated follow primary script pcp_recovery_node was used to
sync standby with new primary node.  However it is sufficient in
follow primary process to just restart standby with new recovery
configuration redirected to the new primary because we use the
"latest" timeline in the configuration file.

Moreover, from PostgreSQL 13, even restarting standby is not
needed. Just changing the recovery configuration and reloading is
enough. With these changes it is expected that the follow primary
process could be significantly faster than before.