[Bug report] Gravitino does not support operations on Iceberg's partitions.

### Version

main branch

### Describe what's wrong

version=1.2.1

### Error message and/or stacktrace

I made a request to https://gravitino.apache.org/docs/1.2.1/api/rest/load-table,

and confirmed that the table indeed has partitions and is an Iceberg table.

However, when I used the API to list partitions, I received an error indicating that the operation is not supported:

https://gravitino.apache.org/docs/1.2.1/api/rest/list-partitions

### How to reproduce

following
https://gravitino.apache.org/docs/1.2.0/lakehouse-iceberg-catalog/#table-partitions

### Additional context

_No response_

Start by reproducing the issue using the Iceberg table-partitions instructions and compare the REST load-table and list-partitions requests documented for version 1.2.1. Trace where the list-partitions request reports that the operation is unsupported, then verify that partition listing works for Iceberg tables without that error.

Written by the indexing model from the issue text.