`setuptools` 82.0.0 does not contain `pkg_resources` anymore

[FlorianSW]

When using the cloudformation-cli with the latest setuptools (which needs to be manually installed, see #1067), which currently is 82.0.1, running any cfn command errors with the following error message:

/test # cfn generate
Traceback (most recent call last):
  File "/usr/local/bin/cfn", line 3, in <module>
    from rpdk.core.cli import main
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/cli.py", line 12, in <module>
    from .build_image import setup_subparser as build_image_setup_subparser
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/build_image.py", line 11, in <module>
    from .project import Project
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/project.py", line 21, in <module>
    from rpdk.core.fragment.generator import TemplateFragment
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/fragment/generator.py", line 14, in <module>
    from rpdk.core.data_loaders import resource_json
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/data_loaders.py", line 9, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'

Steps to reproduce:
Running in docker: docker run -it --rm python:3.13-alpine sh

• install cfn cli: pip3 install cloudformation-cli
• install setuptools: pip3 install setuptools
• run cfn generate

Expected result:
Some valid cfn error message, such as Project file /.rpdk-config not found. Have you run 'init' or in a wrong directory?.

Current result:

 # cfn generate
Traceback (most recent call last):
  File "/usr/local/bin/cfn", line 3, in <module>
    from rpdk.core.cli import main
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/cli.py", line 12, in <module>
    from .build_image import setup_subparser as build_image_setup_subparser
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/build_image.py", line 11, in <module>
    from .project import Project
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/project.py", line 21, in <module>
    from rpdk.core.fragment.generator import TemplateFragment
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/fragment/generator.py", line 14, in <module>
    from rpdk.core.data_loaders import resource_json
  File "/usr/local/lib/python3.13/site-packages/rpdk/core/data_loaders.py", line 9, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'

Current workaround:
Install a setuptools version lower or equal than 81.0.0 (pip3 install setuptools==81.0.0).

Background:
setuptools starting with 82.0.0 removes the pkg_resources package, see:

• https://setuptools.pypa.io/en/latest/history.html#v82-0-0
• Remove pkg_resources pypa/setuptools#5007
• https://stackoverflow.com/questions/7446187/no-module-named-pkg-resources/79888812#79888812