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

test/box-luatest/hide_show_prompt_test.lua

-local it = require('test.luatest_helpers.interactive_tarantool')
+local it = require('test.interactive_tarantool')
 
 local t = require('luatest')
 local g = t.group()