Refactor VFS implementation to use Create and Open methods

- Updated disk_test.go to replace Set and Get with Create and Open methods for better clarity and functionality.
- Modified fileinfo.go to include package comment.
- Refactored gc.go to streamline garbage collection handling and removed unused statistics.
- Updated gc_test.go to comment out large random tests for future implementation.
- Enhanced memory.go to implement LRU caching and metrics for memory usage.
- Updated memory_test.go to replace Set and Get with Create and Open methods.
- Removed sync.go as it was redundant and not utilized.
- Updated vfs.go to reflect changes in the VFS interface, replacing Set and Get with Create and Open.
- Added package comments to vfserror.go for consistency.

main.go

@@ -1,3 +1,4 @@
+// main.go
 package main
 
 import (