[breaking] Bump Python requirement to 3.10. (#10434)

- Bump the Python requirement.
- Fix type hints.
- Use loky to avoid deadlock.
- Workaround cupy-numpy compatibility issue on Windows caused by the `safe` casting rule.
- Simplify the repartitioning logic to avoid dask errors.

doc/conf.py

@@ -286,7 +286,7 @@ latex_documents = [
 ]
 
 intersphinx_mapping = {
-    "python": ("https://docs.python.org/3.8", None),
+    "python": ("https://docs.python.org/3.10", None),
     "numpy": ("https://numpy.org/doc/stable/", None),
     "scipy": ("https://docs.scipy.org/doc/scipy/", None),
     "pandas": ("https://pandas.pydata.org/pandas-docs/stable/", None),