fix: replace pkg_resources with importlib

[kemingy]

• related to Rebuild for python 3.13 conda-forge/mosec-feedstock#14

We already release 3.13 since it has compatible ABI as the final release. (this is the default behavior for cibuildwheel).

However, pkg_resources is deprecated.

• https://importlib-resources.readthedocs.io/en/latest/migration.html#pkg-resources-resource-filename

[kemingy]

Both msgpack and msgspec do not have the support for 3.13 for now.

• Add support for >3.12 and no-GIL builds msgpack/msgpack-python#614
• 3.13 support jcrist/msgspec#698

Although numpy and cython already support 3.13.

I'm going to skip mixin tests for 3.13