Warehouse path is always required for Glue catalog, even when there isn't one

The [warehouse](https://github.com/apache/iceberg-rust/blob/c754e27f752a9e2f86180a9b40f69a3d4ab2dae9/crates/catalog/glue/src/catalog.rs#L46) config prop for Glue catalog is required, but it isn't always known or required. The Glue catalog ID is enough in order to resolve metadata locations.

Moreover - I don't think this path is used for anything but protocol (FileIO type) inference? I was able to work around this issue by passing the correct Glue catalog ID (which is the AWS account ID) and `s3://` as the warehouse, with no issue.

In my opinion `warehouse` should be replaced with something like `FileIO` type and only the Glue catalog ID should be required, but for backwards compatibility not passing warehouse should at least be allowed.

Start with crates/catalog/glue/src/catalog.rs around line 46 and trace how the Glue catalog ID and warehouse are used during catalog initialization. Verify the behavior when only the catalog ID is provided, then ensure metadata locations still resolve without a warehouse while preserving the existing configuration behavior.

Written by the indexing model from the issue text.