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/memory/memory.go

@@ -169,11 +169,14 @@ func (m *MemoryFS) Create(key string, size int64) (io.WriteCloser, error) {
 		onClose: func() error {
 			data := buf.Bytes()
 			m.mu.Lock()
+			var accessCount int64 = 0
 			if f, exists := m.files[key]; exists {
 				m.size -= int64(len(f.data))
 				m.LRU.Remove(key)
+				accessCount = f.fileinfo.AccessCount // preserve access count if overwriting
 			}
 			fi := vfs.NewFileInfo(key, int64(len(data)), time.Now())
+			fi.AccessCount = accessCount
 			m.files[key] = &file{
 				fileinfo: fi,
 				data:     data,
@@ -232,6 +235,7 @@ func (m *MemoryFS) Open(key string) (io.ReadCloser, error) {
 		return nil, vfserror.ErrNotFound
 	}
 	f.fileinfo.ATime = time.Now()
+	f.fileinfo.AccessCount++ // Increment access count for LFU
 	m.LRU.MoveToFront(key)
 	dataCopy := make([]byte, len(f.data))
 	copy(dataCopy, f.data)