Support for custom Iceberg catalog name

### Describe the feature
I am currently not able to use my custom Iceberg catalog name, this is because as the documentation states the name `glue_catalog` is hardcoded as the catalog name for Iceberg operations. There should be support for using custom catalog names.

### Describe alternatives you've considered
I don't see any alternatives yet other than changing the source code for dbt-glue on my machine.

### Additional context
[Link to the section in documentation](https://github.com/aws-samples/dbt-glue#iceberg)

### Who will this benefit?
Anyone using the Iceberg connector.

### Are you interested in contributing this feature?
Yes

Search the dbt-glue source for the documented hardcoded `glue_catalog` value, then compare its use with the Iceberg documentation section linked in the issue. Done means Iceberg operations accept a custom catalog name instead of requiring `glue_catalog`, with the usage documented.

Written by the indexing model from the issue text.