Add ability to specify catalog version when using ibm-pak for CASE bundle downloads

[lasseeme]

Feature and motivation

Feature: Add the ability to specify a catalog version (version identifier) when using ibm-pak to download CASE bundles for MAS and its dependencies.

Motivation: Currently, ibm-pak always retrieves CASE bundles from the latest available catalog, which creates significant challenges for airgapped environments and reproducible deployments. While users can specify the MAS core version (e.g., ibm-mas 9.1.8), dependency components like SLS and Truststore Manager are always pulled from the most recent catalog, not from the catalog that was current when that MAS version was released.

This limitation prevents users from:

1. Mirroring historical releases: In April 2026, it's impossible to download the February 2026 catalog's CASE bundles for MAS 9.1.8 and its dependencies, even though that was the tested and validated configuration at release time
2. Ensuring version consistency: Dependencies downloaded today may differ from those available when the MAS version was released, potentially causing compatibility issues
3. Reproducing deployments: Organizations cannot recreate the exact deployment configuration that was used in production or testing at a specific point in time
4. Supporting airgapped environments: Disconnected environments require the ability to mirror the exact image set from a specific catalog release, not a mix of versions from different time periods

Proposed solution: Introduce a --catalog-version parameter that allows users to specify which catalog snapshot to use when downloading CASE bundles, ensuring all components (MAS core and dependencies) come from the same catalog release.

Usage example

oc ibm-pak get ibm-mas --version 9.1.8 --catalog-version v9-260129-amd64

This enhancement would enable consistent, reproducible deployments and proper support for airgapped environments requiring specific historical catalog versions.