[NEW]Fill the API/functionality gap of KVDK::List and Redis::List.

[Chen Cheng]

The problem/use-case that the feature addresses

The Redis::List commands require KVDK::List provide more functions.

Description of the feature

E.g.
Redis::List::LLEN ---> KVDK return the length of the list
Redis::List::LPOS ---> KVDK returns the index of matching elements inside a KVDK::List
etc.