GitLab

* change percentile in CUDARegressionL1loss::BoostFromScore to 0.5

* add huber regression for cuda_exp

* renew tree output on GPU

add test cases for regression objectives

* remove useless changes

* add white space

* fix test_regression

* add (l1) regression objective for cuda_exp

* remove RenewTreeOutputCUDA from CUDARegressionL2loss

* remove mutable and use CUDAVector

* remove white spaces

* remove TODO and document in (#5459)

* add (l2) regression objective for cuda_exp

* fix lint errors

* correct time tag