Correct RESP3 return type Set for SDIFF, SINTER, SUNION, SMEMBERS, SPOP

[zuiderkwast]

The return type of these commands is listed as array, but in RESP3 they return a set reply.

I suspect the reason for this originates from the fact that the reply schema is a JSON schema, and JSON doesn't have sets, so the schemas don't distinguish between arrays and sets.

@guybe7

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[Yury-Fridlyand]

Voting for merging this:

$ redis-cli -3
127.0.0.1:6379> sinter s1
1~ "a"
127.0.0.1:6379> sinter s1
1~ "a"
127.0.0.1:6379> sinter s1 s2
(empty set)
127.0.0.1:6379> smembers s1
1~ "a"
127.0.0.1:6379>