Manage complete cache lifecycle

Implement comprehensive cache lifecycle management focusing on three key aspects:

1. Idempotent Creation: Make cache creation idempotent by returning success for identical configurations and error only for conflicting ones. This enables reliable automation and prevents redundant cache instances.

Example:

impl Cache {
    fn create(&self, config: CacheConfig) -> Result<(), Error> {
        match self.get_existing_config(&config.name) {
            Some(existing) if existing == config => Ok(()), // Identical config
            Some(_) => Err(Error::ConflictingConfig),      // Different config
            None => {
                self.insert_new_cache(config);
                Ok(())
            }
        }
    }
}

1. Efficient Maintenance: Schedule cache maintenance operations (pruning, eviction) at appropriate intervals:
   • Perform heavy operations like eviction during low-activity periods (e.g., during snapshots)
   • Use reasonable intervals for routine checks (e.g., once per second vs every 10ms)
   • Hold locks for minimum duration needed
2. Complete Cleanup: Implement thorough cleanup that removes all artifacts when entries expire:
   • Remove expired values from cache stores
   • Clean up empty key entries in hierarchical caches
   • Walk up cache trees to remove empty branches
   • Consider using weak references for temporary entries

This ensures optimal memory usage and prevents accumulation of stale metadata.