pin setuptools<82 in pip packaging command to prevent pkg_resources removal

[tagaws]

Issue

Companion to aws-cloudformation/cloudformation-cli#[https://github.com/aws-cloudformation/cloudformation-cli/pull/1118]

Problem

cfn submit runs:
pip install --upgrade --requirement requirements.txt --target build/

With no setuptools version constraint, --upgrade pulls setuptools 82+ into the build zip. setuptools 82 removed pkg_resources, breaking cloudformation-cli-python-lib at runtime.

Downgrading setuptools in the dev venv does NOT fix this — cfn submit re-installs fresh into build/ regardless of the venv state.

Changes

• codegen.py _make_pip_command: append setuptools<82 to the pip install command so the build zip never contains a broken setuptools
• setup.py: pin setuptools<82 in install_requires
• templates/requirements.txt: add setuptools<82 so new projects from cfn init have the pin from day one

Testing

• rpdk.log confirms setuptools-81.0.0 installed during packaging (not 82+)
• Unit test test__make_pip_command_pins_setuptools_lt_82 added to codegen_test.py
• End-to-end: cfn submit --dry-run + zip inspection confirms constraint works (Also tested cfn test with sam local deploy working as expected)

[tagaws]

Protects the dev env (venv) from pinning incorrect setuptools version still safe to add a <82 here, although codegen.py is what compiles it into the build: - If someone uses a different build tool or manually runs pip against requirements.txt

[tagaws]

Without this change, a brand new project created with cfn init would get a requirements.txt containing only:

cloudformation-cli-python-lib>=2.1.9

You would still need to pin <82 locally to get cfn init working based on my testing on a fresh instalation without pinning <82 when you run cfn init you will get the following error "ModuleNotFoundError: No module named 'pkg_resources' "

[tagaws]

Issue mentioned here aws-cloudformation/cloudformation-cli#1117