Be a bit more aggressive when cleaning up stale cache directories
- Delete taskArtifactState cache where major version is older than executing version
    - This behaviour remains as before
- Delete intTestHomeDir/worker-1 caches where version is snapshot and is older than tested version
    - This means that if we test a new incoming distribution, then test an older one,
      the older caches will need to be repopulated
    - Note that this does not impact the artifact (repository) cache