tests: add discarder test
tests: add discarder test

  UPDATE tab SET my_set_or_map = my_set_or_map - { key1, key2 }

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