The most common case for validation will be that the wrapper jars are unchanged
from a previous workflow run. In this case, we cache the validated wrapper
checksums to minimise the work required on a subsequent run.
Fixes#172
- All cache keys are now structured as 'gradle-<cache-name>-<protocol-version>
- This ensures that extracted entries are prefixed and versioned consistently
- Avoid using custom cache-key prefix for extracted entries. This should reduce the
churn in integration tests that require some level of cache isolation.