[BP]MB-7353: Remove the small item feature

Change-Id: I24d2e523eab5a7b23bddb13ad0752d346672b599
Reviewed-on: http://review.couchbase.org/25275
Reviewed-by: xiaoqin ma <maxiaoqin2005@gmail.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>