Refactor caching logic and enhance hash generation in steamcache

- Replaced SHA1 hash calculations with SHA256 for improved security and consistency in cache key generation.
- Introduced a new TestURLHashing function to validate the new cache key generation logic.
- Removed outdated hash calculation tests and streamlined the caching process to focus on URL-based hashing.
- Implemented lightweight validation methods in ServeHTTP to enhance performance and reliability of cached responses.
- Added batched time updates in VFS implementations for better performance during access time tracking.

vfs/vfs.go

@@ -69,6 +69,39 @@ func (fi *FileInfo) UpdateAccess() {
 	fi.AccessCount++
 }
 
+// BatchedTimeUpdate provides a way to batch time updates for better performance
+type BatchedTimeUpdate struct {
+	currentTime    time.Time
+	lastUpdate     time.Time
+	updateInterval time.Duration
+}
+
+// NewBatchedTimeUpdate creates a new batched time updater
+func NewBatchedTimeUpdate(interval time.Duration) *BatchedTimeUpdate {
+	now := time.Now()
+	return &BatchedTimeUpdate{
+		currentTime:    now,
+		lastUpdate:     now,
+		updateInterval: interval,
+	}
+}
+
+// GetTime returns the current cached time, updating it if necessary
+func (btu *BatchedTimeUpdate) GetTime() time.Time {
+	now := time.Now()
+	if now.Sub(btu.lastUpdate) >= btu.updateInterval {
+		btu.currentTime = now
+		btu.lastUpdate = now
+	}
+	return btu.currentTime
+}
+
+// UpdateAccessBatched updates the access time using batched time updates
+func (fi *FileInfo) UpdateAccessBatched(btu *BatchedTimeUpdate) {
+	fi.ATime = btu.GetTime()
+	fi.AccessCount++
+}
+
 // GetTimeDecayedScore calculates a score based on access time and frequency
 // More recent and frequent accesses get higher scores
 func (fi *FileInfo) GetTimeDecayedScore() float64 {