Add admin file inspector (#12635)

Download files from *any* bucket/path as an encrypted zip file.

The key is included in the response but can be separated so zip 
and the key doesn't have to be sent on the same channel.

Requires https://github.com/minio/pkg/pull/6

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

@@ -58,6 +58,7 @@ const (
 	storageMetricUpdateMetadata
 	storageMetricReadVersion
 	storageMetricReadAll
+	storageStatInfoFile
 
 	// .... add more
 
@@ -611,6 +612,22 @@ func (p *xlStorageDiskIDCheck) ReadAll(ctx context.Context, volume string, path
 	return p.storage.ReadAll(ctx, volume, path)
 }
 
+func (p *xlStorageDiskIDCheck) StatInfoFile(ctx context.Context, volume, path string) (stat StatInfo, err error) {
+	defer p.updateStorageMetrics(storageStatInfoFile, volume, path)()
+
+	select {
+	case <-ctx.Done():
+		return StatInfo{}, ctx.Err()
+	default:
+	}
+
+	if err = p.checkDiskStale(); err != nil {
+		return StatInfo{}, err
+	}
+
+	return p.storage.StatInfoFile(ctx, volume, path)
+}
+
 func storageTrace(s storageMetric, startTime time.Time, duration time.Duration, path string) madmin.TraceInfo {
 	return madmin.TraceInfo{
 		TraceType: madmin.TraceStorage,