tests: convert foreign_ptr_test to SEASTAR_TEST_CASE
tests: convert foreign_ptr_test to SEASTAR_TEST_CASE

Makes it pass.

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