Iterate backwards on zdiff/zinter/zunion to optimize for zslInsert (#8105)
Iterate backwards on zdiff/zinter/zunion to optimize for zslInsert (#8105)

In the iterator for these functions, we'll traverse the sorted sets
in a reversed way so that largest elements come first. We prefer
this order because it's optimized for insertion in a skiplist, which
is the destination of the elements being iterated in there functions.
ctripcorp/redis,ofirluzon/redis,ofirluzon/redis,charsyam/redis,ofirluzon/redis,charsyam/redis,oranagra/redis,soloestoy/redis,neomantra/redis,yossigo/redis,neomantra/redis,oranagra/redis,PKRoma/redis,soloestoy/redis,soloestoy/redis,yossigo/redis,antirez/redis,ofirluzon/redis,antirez/redis,charsyam/redis,oranagra/redis,neomantra/redis,ctripcorp/redis,yossigo/redis,PKRoma/redis,neomantra/redis,soloestoy/redis,ctripcorp/redis,PKRoma/redis,oranagra/redis,soloestoy/redis,PKRoma/redis,charsyam/redis,charsyam/redis,antirez/redis,yossigo/redis,antirez/redis,oranagra/redis,yossigo/redis,neomantra/redis,ofirluzon/redis,PKRoma/redis,ctripcorp/redis