Background:

Redis includes the replication buffer size but not the client output buffers of the replicas. When KeyDB began using the replication buffer as the client output buffer and eliminated the extra copy we now have diverging behavior with Redis.

The fix here is to include the base replication buffer size towards maxmem but exclude any extra dynamic growth which occurs when we are emulating the expanding client output buffer behavior. This gets us back to parity with Redis' memory trackingl.