drop cython language_level on v3.0.0

[bjlittle]

Once cython 3.0.0 lands:

• drop use of the cython language_level compiler directive (3str will be the default behaviour)
• add a min pin for cython>=3.0 for conda and PyPI deps
• address warning: #warning "Using deprecated NumPy API, disable it with " "#define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-Wcpp], see
  • https://cython.readthedocs.io/en/latest/src/userguide/migrating_to_cy30.html?highlight=NPY_NO_DEPRECATED_API#numpy-c-api
  • https://cython.readthedocs.io/en/latest/src/tutorial/numpy.html?highlight=import_array#adding-types

See https://github.com/cython/cython/milestone/58

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[github-actions]

In order to maintain a backlog of relevant issues, we automatically label them as stale after 500 days of inactivity.

If this issue is still important to you, then please comment on this issue and the stale label will be removed.

Otherwise this issue will be automatically closed in 28 days time.

[HGWright]

still relevant