Gradient boosting - Adapt tests to version xgboost=2; move xgboost/catboost to regular requirements

[PrimozGodec]

Issue

Xgboost released version 2.0.0, which changes some internal interfaces and breaks our tests.

Description of changes

Adapt tests to 2.0.0.

Also, now Xgboost packs Libomp in wheels for Macos (I think it was a primary reason for keeping Xgbosot and Catboost optional dependency). I suggest including both as a mandatory dependency. They are packed in Installers and part of a conda-forge package already/anyway.

Includes

• Code changes
• Tests
• Documentation

[markotoplak]

Does new xgboost only break tests or also widgets? If the latter, we will perhaps need 3.36.1.

[markotoplak]

Oh, I now see there were just the tests.

[PrimozGodec]

@markotoplak, no need for 3.36.1. It breaks only tests.

I decided to fix it to xgboost>=2 since it doesn't hurt. If we don't want to do this, we will need to write two versions of tests.

[markotoplak]

Can you also update meta.yaml?

Conda-forge only has xgboost 1.7 for now, but that is likely not much of a problem. Anything that relies on building Orange though conda build would fail until they release 2.0. Maybe that is not much of a problem.

[PrimozGodec]

I updated meta.yaml. I didn't fix the version there. I think it should work for now.