GitLab

* [R-package] move more finalizer logic intoo C++ side

* add C finalizers

* use gc()

* put skip() back

* Update R-package/tests/testthat/test_lgb.Booster.R
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>