Enhance file metadata tracking and garbage collection logic

- Added AccessCount field to FileInfo struct for improved tracking of file access frequency.
- Updated NewFileInfo and NewFileInfoFromOS functions to initialize AccessCount.
- Modified DiskFS and MemoryFS to preserve and increment AccessCount during file operations.
- Enhanced garbage collection methods (LRU, LFU, FIFO, Largest, Smallest, Hybrid) to utilize AccessCount for more effective space reclamation.

vfs/disk/disk.go

@@ -242,10 +242,12 @@ func (d *DiskFS) Create(key string, size int64) (io.WriteCloser, error) {
 
 	// Check again after lock
 	d.mu.Lock()
+	var accessCount int64 = 0
 	if fi, exists := d.info[key]; exists {
 		d.size -= fi.Size()
 		d.LRU.Remove(key)
 		delete(d.info, key)
+		accessCount = fi.AccessCount // preserve access count if overwriting
 		path := filepath.Join(d.root, key)
 		os.Remove(path) // Ignore error, as file might not exist or other issues
 	}
@@ -274,6 +276,7 @@ func (d *DiskFS) Create(key string, size int64) (io.WriteCloser, error) {
 
 			d.mu.Lock()
 			finfo := vfs.NewFileInfoFromOS(fi, key)
+			finfo.AccessCount = accessCount
 			d.info[key] = finfo
 			d.LRU.Add(key, finfo)
 			d.size += n
@@ -381,6 +384,7 @@ func (d *DiskFS) Open(key string) (io.ReadCloser, error) {
 		return nil, vfserror.ErrNotFound
 	}
 	fi.ATime = time.Now()
+	fi.AccessCount++ // Increment access count for LFU
 	d.LRU.MoveToFront(key)
 	d.mu.Unlock()