Fix hgetf/hsetf reply type by returning string

[tezc]

If encoding is listpack, hgetf and hsetf commands reply field value type as integer.
This PR fixes it by returning string.

Problematic cases:

127.0.0.1:6379> hset hash one 1
(integer) 1
127.0.0.1:6379> hgetf hash fields 1 one
1) (integer) 1
127.0.0.1:6379> hsetf hash GETOLD fvs 1 one 2
1) (integer) 1
127.0.0.1:6379> hsetf hash DOF GETNEW fvs 1 one 2
1) (integer) 2

Additional fixes:

• hgetf/hsetf command description text

Fixes #13261, #13262

[LiorKogan]

Shouldn't it be 7.4 (for all HFE commands)?

[tezc]

I'm aware of this and we need to change it for all hfe commands. I'll address in a future PR.