Mljar-supervised

Many small improvements.

A lot of small tweaks and improvements :)

Enhancements
- 300 Add step with k-means additional features
- 299 Add Boost On Errors step
- 154 Sample weight available
- 229 Sort leaderboard (disabled for now for debug purposes)

Bug fixes
- 301 Fix storing unique keys in mljar tuner only for trained models
- 275 248 small fixes

Bug fixes
- 293 Typo in `is_scale_needed`
- 277 Fix problem with unit data
- 285 Restricted characters in LightGBM

Bug fixes
- 292 Remove unused params from CatBoost

Enhancements
- 291 Disable loo encoding
- 290 improve ordering in hill climbing
- 287 replace mix_encoding with integet_encoding