Optimize listing with leaf check offloaded to posix (#7541)

Other listing optimizations include

- remove double sorting while filtering object entries
- improve error message when upload-id is not in quorum
- use jsoniter for full unmarshal json, instead of gjson
- remove unused code

cmd/storage-rest-client.go

@@ -315,11 +315,12 @@ func (client *storageRESTClient) ReadFile(volume, path string, offset int64, buf
 }
 
 // ListDir - lists a directory.
-func (client *storageRESTClient) ListDir(volume, dirPath string, count int) (entries []string, err error) {
+func (client *storageRESTClient) ListDir(volume, dirPath string, count int, leafFile string) (entries []string, err error) {
 	values := make(url.Values)
 	values.Set(storageRESTVolume, volume)
 	values.Set(storageRESTDirPath, dirPath)
 	values.Set(storageRESTCount, strconv.Itoa(count))
+	values.Set(storageRESTLeafFile, leafFile)
 	respBody, err := client.call(storageRESTMethodListDir, values, nil, -1)
 	if err != nil {
 		return nil, err