[#4584]feat(catalog-iceberg) Support loading custom catalog as backend in Gravitino Iceberg catalog

[theoryxu]

What changes were proposed in this pull request?

Support loading custom catalog as backend in Gravitino Iceberg catalog

Why are the changes needed?

Fix: #4584

Does this PR introduce any user-facing change?

add a property key

How was this patch tested?

add UT
manual test

[theoryxu]

In my case, I can reuse the JDBC catalog configurations for my custom catalog, but this approach doesn't cover other custom catalogs.

Now, we need to enumerate all configuration keys in IcebergCatalogPropertiesMetadata.

Should we accept all configurations, only those with certain prefixes, or wait until we encounter other cases?

@FANNG1 WDYT？

[FANNG1]

In my case, I can reuse the JDBC catalog configurations for my custom catalog, but this approach doesn't cover other custom catalogs.

Now, we need to enumerate all configuration keys in IcebergCatalogPropertiesMetadata.

Should we accept all configurations, only those with certain prefixes, or wait until we encounter other cases?

@FANNG1 WDYT？

I prefer to delay supporting the custom catalog backend for the Gravitino Iceberg catalog until there are real requirements.