fix: allow diskInfo at storageRPC to be cached (#19112)

Bonus: convert timedValue into a typed implementation

cmd/xl-storage-disk-id-check.go

@@ -89,7 +89,7 @@ type xlStorageDiskIDCheck struct {
 	health       *diskHealthTracker
 	healthCheck  bool
 
-	metricsCache timedValue
+	metricsCache *timedValue[DiskMetrics]
 	diskCtx      context.Context
 	diskCancel   context.CancelFunc
 }
@@ -97,7 +97,7 @@ type xlStorageDiskIDCheck struct {
 func (p *xlStorageDiskIDCheck) getMetrics() DiskMetrics {
 	p.metricsCache.Once.Do(func() {
 		p.metricsCache.TTL = 5 * time.Second
-		p.metricsCache.Update = func() (interface{}, error) {
+		p.metricsCache.Update = func() (DiskMetrics, error) {
 			diskMetric := DiskMetrics{
 				LastMinute: make(map[string]AccElem, len(p.apiLatencies)),
 				APICalls:   make(map[string]uint64, len(p.apiCalls)),
@@ -111,12 +111,8 @@ func (p *xlStorageDiskIDCheck) getMetrics() DiskMetrics {
 			return diskMetric, nil
 		}
 	})
-	m, _ := p.metricsCache.Get()
-	diskMetric := DiskMetrics{}
-	if m != nil {
-		diskMetric = m.(DiskMetrics)
-	}
 
+	diskMetric, _ := p.metricsCache.Get()
 	// Do not need this value to be cached.
 	diskMetric.TotalErrorsTimeout = p.totalErrsTimeout.Load()
 	diskMetric.TotalErrorsAvailability = p.totalErrsAvailability.Load()
@@ -180,9 +176,10 @@ func (e *lockedLastMinuteLatency) total() AccElem {
 
 func newXLStorageDiskIDCheck(storage *xlStorage, healthCheck bool) *xlStorageDiskIDCheck {
 	xl := xlStorageDiskIDCheck{
-		storage:     storage,
-		health:      newDiskHealthTracker(),
-		healthCheck: healthCheck && globalDriveMonitoring,
+		storage:      storage,
+		health:       newDiskHealthTracker(),
+		healthCheck:  healthCheck && globalDriveMonitoring,
+		metricsCache: newTimedValue[DiskMetrics](),
 	}
 
 	xl.totalWrites.Store(xl.storage.getWriteAttribute())