1.9.0
merged upstream-master into enh/tree
Fix color conversion to rgb hexstring (#33845)
Fix: improve speed of trees with MAE criterion from O(n^2) to O(n log n) (#32100)
ENH Support for monotonic trees with missing values (#27630)
MNT Fix typos found by typos (#33916)
FEA Add support for missing values in tree estimators with `criterion="absolute_error"` by greatly simplifying the logic (#32119)
MNT remove tree DOUBLE and DTYPE (#33948)