build: Add support for NumPy 2.0 wheels

* Add numpy>=2.0.0 to build-system requires to build NumPy 1.x and 2.x compatible
  wheels.
   - c.f. https://numpy.org/doc/stable/dev/depending_on_numpy.html#numpy-2-0-specific-advice
   - As NumPy 2.0 is Python 3.9+, also need to conditionally support 'oldest-supported-numpy'
     for Python 3.8.
* Remove wheel from build-system requires as it is never required and injected
  automatically by setuptools only when needed.
   - c.f. https://learn.scientific-python.org/development/guides/packaging-classic/

Author: matthewfeickert

pyproject.toml

@@ -1,3 +1,8 @@
 [build-system]
-requires = ["setuptools", "wheel", "oldest-supported-numpy", "cython>=0.23"]
-build-backend = "setuptools.build_meta"
+requires = [
+    "setuptools>=42",
+    "oldest-supported-numpy; python_version < '3.9'",
+    "numpy>=2.0.0; python_version >= '3.9'",
+    "cython>=0.23"
+]
+build-backend = "setuptools.build_meta"