Incompatible with Python 3.12

[abbasyadollahi]

The pyformance package is incompatible with a freshly installed Python 3.12 virtual environment, unless setuptools is also installed.

Steps to reproduce:

$ python3.12 -m venv env
$ source env/bin/activate
$ pip install pyformance
$ pip list

Package Version
------- -------
pip     24.0

Python 3.12.4 (main, Jun  6 2024, 18:26:44) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from pyformance import MetricsRegistry
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/user/env/lib/python3.12/site-packages/pyformance/__init__.py", line 1, in <module>
    __import__('pkg_resources').declare_namespace(__name__)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
ModuleNotFoundError: No module named 'pkg_resources'