rpc: allow handler to receive non default constructable types
rpc: allow handler to receive non default constructable types

Currently it is not possible because a type is instantiated before been
deserialized. Fix that by allocating space for an object by using
std::aligned_storage.

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