Prune wdclient Functions (#8855)

* chore(weed/wdclient): prune unused functions

* chore(weed/wdclient): prune test-only functions and associated tests

* chore(weed/wdclient): remove dead cursor field

The cursor field and its initialization are no longer used after
the removal of getLocationIndex.

---------

Co-authored-by: Chris Lu <chris.lu@gmail.com>

weed/wdclient/vid_map.go

@@ -15,10 +15,6 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 )
 
-const (
-	maxCursorIndex = 4096
-)
-
 type HasLookupFileIdFunction interface {
 	GetLookupFileIdFunction() LookupFileIdFunctionType
 }
@@ -41,7 +37,6 @@ type vidMap struct {
 	vid2Locations   map[uint32][]Location
 	ecVid2Locations map[uint32][]Location
 	DataCenter      string
-	cursor          int32
 	cache           atomic.Pointer[vidMap]
 }
 
@@ -50,20 +45,9 @@ func newVidMap(dataCenter string) *vidMap {
 		vid2Locations:   make(map[uint32][]Location),
 		ecVid2Locations: make(map[uint32][]Location),
 		DataCenter:      dataCenter,
-		cursor:          -1,
 	}
 }
 
-func (vc *vidMap) getLocationIndex(length int) (int, error) {
-	if length <= 0 {
-		return 0, fmt.Errorf("invalid length: %d", length)
-	}
-	if atomic.LoadInt32(&vc.cursor) == maxCursorIndex {
-		atomic.CompareAndSwapInt32(&vc.cursor, maxCursorIndex, -1)
-	}
-	return int(atomic.AddInt32(&vc.cursor, 1)) % length, nil
-}
-
 func (vc *vidMap) isSameDataCenter(loc *Location) bool {
 	if vc.DataCenter == "" || loc.DataCenter == "" || vc.DataCenter != loc.DataCenter {
 		return false