fix entrypoints installation by limiting setuptools compatiblity

[alexrashed]

Motivation

With setuptools==75.2.0, plux has issues when restoring the entrypoints on the installation of source distributions.
This is caused by pypa/setuptools#4647, it might be specifically relate to this comment. It definitely is caused by the fact that the egg_info command and the egg2dist is not called anymore.

I also tried to dive into this with a hack implemented in ffb1ad9 which will be taken over by @thrau.

In LocalStack, we are mitigating this issue by introducing a limit in the build-system.requires: localstack/localstack#11715

However, this only fixes the issue in upcoming releases, the source distributions out there won't be affected by this change.
This is why plux itself should declare that it is not compatible with the latest release of setuptools.

Changes

This PR introduces setuptools as an install dependency (which it is and always was) and limits the version to <=75.1.0 (which is the latest compatible version).
This change can be reverted as soon as plux is compatible with the latest version of setuptools again.

Testing

I verified that this fix by executing the following steps / scripts:

• Use the local version of plux in one of the test projects:

  diff --git a/tests/cli/projects/pyproject/pyproject.toml b/tests/cli/projects/pyproject/pyproject.toml
  index 54c5728..9f69017 100644
  --- a/tests/cli/projects/pyproject/pyproject.toml
  +++ b/tests/cli/projects/pyproject/pyproject.toml
  @@ -1,5 +1,5 @@
   [build-system]
  -requires = ["setuptools", "wheel", "plux"]
  +requires = ["setuptools", "wheel", "plux@file:///home/localstack/Repos/plux"]
   build-backend = "setuptools.build_meta"
   
   [project]

• Apply the change in this PR
• Run the following script to verify that the entrypoints are correctly available after installing the source distribution:

  #!/bin/bash
  set -e
  
  # make sure setuptools on the system and in the venv is up to date.
  pip install --upgrade setuptools
  
  # create a test-venv and also ugprade setuptools
  cd tests/cli/projects/pyproject/
  rm -rf setuptools-test-venv
  python3 -m venv setuptools-test-venv
  source setuptools-test-venv/bin/activate
  pip install --upgrade setuptools
  
  # build the project
  rm -rf dist
  pip install build
  python3 -m build
  
  # install the source distribution with the local plux reference
  pip install --no-cache dist/test_project-0.1.0.tar.gz
  
  # check if the entryponts have been created / print the output:
  cat setuptools-test-venv/lib/python3.11/site-packages/test_project-0.1.0.dist-info/entry_points.txt

  The path in the last line might need to be adjusted based on the Python version.

[thrau]

as discussed we will merge this as a stop-gap solution, and i'll try to follow up with a proper fix ASAP.

the issue adding this dependency in this way is that actually setuptools isn't even a runtime dependency of plux, and therefore shouldn't be part of install_requires. secondly, i'm not sure what the exact implications of this constraints are for certain build environments. it's very hard for me to predict the impact of it, so just want to make sure we move away from it quickly.