GitLab

* initial changes

* initial version

* better handling of cases

* warn only with positive threshold

* remove early_stopping_threshold from high-level functions

* remove remaining early_stopping_threshold

* update test to use callback

* better handling of cases

* rename threshold to min_delta

enhance parameter description

update tests

* Apply suggestions from code review
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* reduce num_boost_round in tests

* Apply suggestions from code review
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* trigger ci
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>
Co-authored-by: Nikita Titov <nekit94-12@hotmail.com>