Motivation

Run test with numpy>=1.24.3

Suggestion

Separate MXNet, scikit-optimize, and shap from optuna/optuna and move tesets to optuna/optuna-integration
We need to fix following files:

• tests/importance_tests/test_init.py
• tests/integration_tests/test_integration.py
• tests/integration_tests/test_shap.py
• tests/integration_tests/test_skopt.py
• tests/integration_tests/test_mxnet.py

Additional context (optional)

Currently, NumPy version is fixed to be smaller than 1.24.0 since some libraries used in integrations are incompatible with them.