Issue
storageClasses.determineStorageClasses() relies on a large series of env string matches across CONFIG_JSON, STORAGECLASS, and PYTEST_PARAMS. This is hard to maintain and tied to naming conventions.

Steps to reproduce
1. Review determineStorageClasses() in vars/storageClasses.groovy.
2. Observe multiple nested string contains checks.

Expected result
Storage class detection uses JOB_METADATA clusterRequirements or a small mapping table.

Actual result
Heuristic string matching across multiple env vars.

Plan

• Prefer JOB_METADATA.clusterRequirements.storageClasses as the source of truth.
• If fallback is needed, use a centralized mapping table (regex->shortName).
• Reduce env var usage to a single structured input where possible.