remove serializing WalkDir() across all buckets/prefixes on SSDs (#17707)

slower drives get knocked off because they are too slow via 
active monitoring, we do not need to block calls arbitrarily.

Serializing adds latencies for already slow calls, remove
it for SSDs/NVMEs

Also, add a selection with context when writing to `out <-`
channel, to avoid any potential blocks.

internal/disk/disk.go

@@ -23,15 +23,20 @@ package disk
 // Files - total inodes available
 // Ffree - free inodes available
 // FSType - file system type
+// Major - major dev id
+// Minor - minor dev id
+// Devname - device name
 type Info struct {
-	Total  uint64
-	Free   uint64
-	Used   uint64
-	Files  uint64
-	Ffree  uint64
-	FSType string
-	Major  uint32
-	Minor  uint32
+	Total      uint64
+	Free       uint64
+	Used       uint64
+	Files      uint64
+	Ffree      uint64
+	FSType     string
+	Major      uint32
+	Minor      uint32
+	Name       string
+	Rotational *bool
 }
 
 // DevID is the drive major and minor ids