Add clean_group_container_caches() to safely clean Group Containers:
- Skip Apple-owned containers (com.apple.*, group.com.apple.*, systemgroup.com.apple.*)
- For protected apps: only clean Logs directories
- For non-protected apps: clean Logs, tmp, and Caches
- Add symlink checks to prevent path traversal
- Respect whitelist and should_protect_path checks
- Integrate with clean_sandboxed_app_caches flow
Also add symlink checks in process_container_cache() for consistency.
Includes 4 BATS tests covering protected apps, whitelist,
system containers, and empty results handling.