Gradle build cache (~/.gradle/caches) is now protected by default whitelist,
similar to Maven repository. This prevents unintentional deletion of large
dependency caches that take time and bandwidth to re-download.
- Add ~/.gradle/caches/* and ~/.gradle/daemon/* to DEFAULT_WHITELIST_PATTERNS
- Remove Gradle cleanup from clean_dev_jvm() function
- Users can disable protection via 'mo clean --whitelist' if needed
Fixes#408