virtio: reduce rx allocations when preparing buffers (part 1)
virtio: reduce rx allocations when preparing buffers (part 1)

Instead of returning a vector of buffer chains, return an iterator
range that will produce those vectors on the fly, removing the vector
allocation.

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