minor: Make `CatalogBuilder.0` more explicit

### Is your feature request related to a problem or challenge?

For the different `CatalogBuilder`s, instead of calling `catalog_builder.0` to get the config we can add a helper function like `catalog_builder.catalog_config()` to retrieve.

### Describe the solution you'd like

_No response_

### Willingness to contribute

None

Search the Rust source for the different CatalogBuilder definitions and each catalog_builder.0 use. Read how the builder stores and exposes its configuration, then check all affected callers. Done means configuration retrieval uses a named helper consistently and the relevant tests or project checks pass.

Written by the indexing model from the issue text.