migration_manager: Convert announce_new_column_family() to C++
migration_manager: Convert announce_new_column_family() to C++

Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@cloudius-systems.com>

kangkot/scylla,phonkee/scylla,rluta/scylla,phonkee/scylla,aruanruan/scylla,tempbottle/scylla,phonkee/scylla,capturePointer/scylla,avikivity/scylla,shaunstanislaus/scylla,bowlofstew/scylla,gwicke/scylla,aruanruan/scylla,raphaelsc/scylla,gwicke/scylla,scylladb/scylla,glommer/scylla,kjniemi/scylla,eklitzke/scylla,asias/scylla,avikivity/scylla,justintung/scylla,rentongzhang/scylla,eklitzke/scylla,acbellini/scylla,stamhe/scylla,kjniemi/scylla,eklitzke/scylla,senseb/scylla,capturePointer/scylla,glommer/scylla,kangkot/scylla,aruanruan/scylla,dwdm/scylla,victorbriz/scylla,bowlofstew/scylla,gwicke/scylla,shaunstanislaus/scylla,capturePointer/scylla,rluta/scylla,linearregression/scylla,acbellini/scylla,wildinto/scylla,guiquanz/scylla,respu/scylla,justintung/scylla,asias/scylla,rentongzhang/scylla,guiquanz/scylla,kangkot/scylla,victorbriz/scylla,victorbriz/scylla,glommer/scylla,bowlofstew/scylla,rentongzhang/scylla,respu/scylla,raphaelsc/scylla,duarten/scylla,avikivity/scylla,rluta/scylla,raphaelsc/scylla,linearregression/scylla,respu/scylla,stamhe/scylla,wildinto/scylla,stamhe/scylla,scylladb/scylla,asias/scylla,justintung/scylla,kjniemi/scylla,scylladb/scylla,tempbottle/scylla,wildinto/scylla,senseb/scylla,guiquanz/scylla,scylladb/scylla,duarten/scylla,shaunstanislaus/scylla,duarten/scylla,senseb/scylla,dwdm/scylla,dwdm/scylla,linearregression/scylla,tempbottle/scylla,acbellini/scylla