Streams: XADD MAXLEN implementation.
Streams: XADD MAXLEN implementation.

The core of this change is the implementation of stream trimming, and
the resulting MAXLEN option of XADD as a trivial result of having
trimming functionalities. MAXLEN already works but in order to be more
efficient listpack GC should be implemented, currently marked as a TODO
item inside the comments.

charsyam/redis,charsyam/redis,neomantra/redis,PKRoma/redis,antirez/redis,nnog/redis,GitHubMota/redis,GitHubMota/redis,pmem/redis,charsyam/redis,charsyam/redis,pmem/redis,rogerchina/redis,soveran/redis,GitHubMota/redis,PKRoma/redis,GitHubMota/redis,soveran/redis,oranagra/redis,rogerchina/redis,antirez/redis,yossigo/redis,pmem/redis,Sciumo/redis,soveran/redis,neomantra/redis,soloestoy/redis,rogerchina/redis,PKRoma/redis,Sciumo/redis,rogerchina/redis,soloestoy/redis,ofirluzon/redis,ctripcorp/redis,yossigo/redis,ctripcorp/redis,nnog/redis,oranagra/redis,oranagra/redis,neomantra/redis,ctripcorp/redis,spinlock/redis,spinlock/redis,yossigo/redis,nnog/redis,ofirluzon/redis,soloestoy/redis,yossigo/redis,PKRoma/redis,neomantra/redis,antirez/redis,nnog/redis,soveran/redis,antirez/redis,ofirluzon/redis,soloestoy/redis,Sciumo/redis,oranagra/redis,soloestoy/redis,spinlock/redis,ctripcorp/redis,yossigo/redis,Sciumo/redis,pmem/redis,PKRoma/redis,oranagra/redis,charsyam/redis,ofirluzon/redis,spinlock/redis,neomantra/redis,ofirluzon/redis