[pgAdmin][RM4633] Bad view in partitioned tables

Attached is the patch to support the view part of the multilevel partitions. Users can perform all the operations except creating the partitions as a partitioned table. Users can create a partition table separately and attach it as a partition of another partition table.

There are two problems mentioned in the RM. I have fixed the first one and we won't fix the second problem as by design we decided to show Partitions like Schema->Table->Partitions

Please review it.

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