test: mv interactive_tarantool.lua to ./test/ dir

The ./test/luatest_helpers/interactive_tarantool.lua module is not
a luatest helper. So moving it to the ./test/ dir and removing empty
./test/luatest_helpers/.

NO_DOC=testing stuff
NO_TEST=testing stuff
NO_CHANGELOG=testing stuff

(cherry picked from commit 5493db7c)