Implement more Hash apis.

[bigboss2063]

The Hash structure already supports some commonly used APIs, like HSet, HGet, etc. You can implement more apis for it.

API	Explanation	assigned	done
HSET key field value	Set the value of a field in a hash.	@bigboss2063	✅
HGET key field	Get the value of a field in a hash.	@bigboss2063	✅
HMSET key field value [field value ...]	Set multiple fields and values in a hash.	@bigboss2063	✅
HMGET key field [field ...]	Get the values of one or more fields in a hash.	@bigboss2063	✅
HDEL key field [field ...]	Delete one or more fields from a hash.	@bigboss2063	✅
HEXISTS key field	Check if a field exists in a hash.	@bigboss2063	✅
HGetAll key	Get all the fileds and the values in a hash.	@bigboss2063	✅
HLEN key	Get the number of fields in a hash.	@99HU	✅
HKEYS key	Get all the field names in a hash.	@99HU	✅
HVALS key	Get all the values in a hash.	@99HU	✅
HStrLen key field	Get the length of value of a field in a hash	@99HU	✅

Anyone who wants to implement other api is welcome to comment below!

现在 Hash 数据结构已经实现了一些常用的接口，比如 HSet、HGet 等等。可以为它实现更多的接口。

指令	解释	承接人	是否完成
HSET key field value	设置哈希表中字段的值。	@bigboss2063	✅
HGET key field	获取哈希表中字段的值。	@bigboss2063	✅
HMSET key field value [field value ...]	同时设置哈希表中多个字段的值。	@bigboss2063	✅
HMGET key field [field ...]	获取哈希表中一个或多个字段的值。	@bigboss2063	✅
HDEL key field [field ...]	删除哈希表中一个或多个字段。	@bigboss2063	✅
HEXISTS key field	检查哈希表中是否存在指定的字段。	@bigboss2063	✅
HGetAll key	获取哈希表中的所有字段和值。	@bigboss2063	✅
HLEN key	获取哈希表中字段的数量	@99HU	✅
HKEYS key	获取哈希表中所有字段。	@99HU	✅
HVALS key	获取哈希表中所有字段的值	@99HU	✅
HStrLen key field	获取哈希表中字段的值对应的长度	@99HU	✅

还有想实现其他接口的朋友欢迎在下面评论出来！

[99HU]

I Iintend to implement these commands：
HLEN、HKEYS 、HVALS、HVALS