service: Implement query_state:: get_client_state() and get_timestamp()
service: Implement query_state:: get_client_state() and get_timestamp()

Needed by query_options and query_processor.

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