Run mrbgem and core tests on minimum dependencies.
Solves #2355.

In test drivers:
* Uses `mrb_t_pass_result` to check and pass test result to main `mrb_state`.
* Adds `mrb_init_test_driver` to init test `mrb_state`.
Merge pull request #2458 from take-cheeze/min_dep_test

Support minimum dependency test.