Use callback in LGBM.train.

[ChiahungTai]

Description

Use callback in LGBM.train.

Motivation and Context

Use callback in LGBM.train. The usage of auguments early_stopping_rounds, verbose_eval, evals_result are not suggested.

How Has This Been Tested?

<! --- Put an x in all the boxes that apply: --->

• Pass the test by running: pytest qlib/tests/test_all_pipeline.py under upper directory of qlib.
• If you are adding a new feature, test on your own test scripts.

Screenshots of Test Results (if appropriate):

1. Pipeline test:
2. Your own tests:

Types of changes

• Fix bugs
• Add new feature
• Update documentation

[you-n-g]

Thanks! It looks more flexible now :)