core: add non-vectored data_sink::put() specialization
core: add non-vectored data_sink::put() specialization

Often the caller doesn't have a vector, just a single buffer, so allow
the implementation to optimize for that.

hongliangzhao/seastar,flashbuckets/seastar,avikivity/scylla,shyamalschandra/seastar,joerg84/seastar,ducthangho/imdb,rentongzhang/scylla,norcimo5/seastar,joerg84/seastar,phonkee/scylla,victorbriz/scylla,kjniemi/scylla,chunshengster/seastar,acbellini/seastar,acbellini/seastar,justintung/scylla,kjniemi/seastar,slivne/seastar,leejir/seastar,jonathanleang/seastar,eklitzke/scylla,scylladb/scylla,stamhe/scylla,linearregression/scylla,stamhe/scylla,shyamalschandra/seastar,acbellini/seastar,duarten/scylla,jonathanleang/seastar,wildinto/seastar,wildinto/scylla,scylladb/scylla-seastar,bowlofstew/seastar,tempbottle/scylla,anzihenry/seastar,raphaelsc/scylla,respu/scylla,linearregression/seastar,glommer/scylla,aruanruan/scylla,norcimo5/seastar,syuu1228/seastar,rentongzhang/scylla,eklitzke/scylla,bowlofstew/seastar,dwdm/seastar,eklitzke/scylla,wildinto/scylla,respu/scylla,koolhazz/seastar,acbellini/scylla,duarten/scylla,dwdm/scylla,wildinto/seastar,dreamsxin/seastar,raphaelsc/scylla,kangkot/scylla,shaunstanislaus/scylla,sjperkins/seastar,kangkot/scylla,stamhe/seastar,capturePointer/scylla,bowlofstew/scylla,phonkee/scylla,acbellini/scylla,guiquanz/scylla,kjniemi/scylla,wildinto/scylla,kjniemi/scylla,senseb/scylla,gwicke/scylla,asias/scylla,kangkot/scylla,xtao/seastar,stamhe/scylla,rluta/scylla,scylladb/seastar,glommer/scylla,slivne/seastar,printedheart/seastar,raphaelsc/seastar,acbellini/scylla,chunshengster/seastar,kjniemi/seastar,scylladb/scylla-seastar,raphaelsc/scylla,glommer/scylla,bowlofstew/scylla,mixja/seastar,anzihenry/seastar,duarten/scylla,dreamsxin/seastar,norcimo5/seastar,dwdm/seastar,raphaelsc/seastar,avikivity/scylla,linearregression/seastar,sjperkins/seastar,ducthangho/imdb,avikivity/seastar,scylladb/seastar,leejir/seastar,kjniemi/seastar,rluta/scylla,scylladb/scylla-seastar,rentongzhang/scylla,avikivity/scylla,xtao/seastar,flashbuckets/seastar,victorbriz/scylla,shyamalschandra/seastar,bzero/seastar,gwicke/scylla,linearregression/scylla,cloudius-systems/seastar,dwdm/scylla,tempbottle/seastar,leejir/seastar,linearregression/scylla,syuu1228/seastar,stamhe/seastar,syuu1228/seastar,mixja/seastar,printedheart/seastar,tempbottle/seastar,bzero/seastar,guiquanz/scylla,wildinto/seastar,senseb/scylla,tempbottle/seastar,gwicke/scylla,capturePointer/scylla,sjperkins/seastar,scylladb/scylla,shaunstanislaus/scylla,cloudius-systems/seastar,mixja/seastar,asias/scylla,rluta/scylla,dreamsxin/seastar,scylladb/scylla,aruanruan/scylla,tempbottle/scylla,dwdm/seastar,koolhazz/seastar,cloudius-systems/seastar,joerg84/seastar,slivne/seastar,stamhe/seastar,justintung/scylla,aruanruan/scylla,hongliangzhao/seastar,scylladb/scylla,victorbriz/scylla,avikivity/seastar,guiquanz/scylla,xtao/seastar,scylladb/seastar,respu/scylla,bowlofstew/scylla,printedheart/seastar,flashbuckets/seastar,senseb/scylla,asias/scylla,linearregression/seastar,hongliangzhao/seastar,avikivity/seastar,raphaelsc/seastar,koolhazz/seastar,jonathanleang/seastar,justintung/scylla,bzero/seastar,chunshengster/seastar,dwdm/scylla,ducthangho/imdb,shaunstanislaus/scylla,anzihenry/seastar,bowlofstew/seastar,tempbottle/scylla,capturePointer/scylla,phonkee/scylla