[Build] Implement install_requirements.sh with Python

[python3kgae]

Move the details of install_requirements.sh into install_requirements.py. Then, call install_requirements.py from install_requirements.sh.

This will avoid duplication when adding Windows version of installing_requirements.

This is for issue #4661.

Release Note: Moved the main install_requirements.sh logic into install_requirements.py so that it can also run on Windows.

Test Plan:
Tested on a mac.

Ran ./install_requirements.sh --pybind xnnpack under python 3.10, and it completed successfully. To make sure that xnnpack was actually installed, I manually ran the steps from the notebook at https://colab.research.google.com/drive/1qpxrXC3YdJQzly3mRg-4ayYiOjC6rue3, and it passed.

When running the same in a clean python 3.8 environment, it failed as expected with

% ./install_requirements.sh --pybind xnnpack
Collecting packaging
Using cached packaging-24.1-py3-none-any.whl.metadata (3.2 kB)
Using cached packaging-24.1-py3-none-any.whl (53 kB)
Installing collected packages: packaging
Successfully installed packaging-24.1
ERROR: ExecuTorch does not support python version 3.8.19: must satisfy ">=3.10"

Also tested under WSL and native Windows.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/4748

• 📄 Preview Python docs built from this PR

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✅ You can merge normally! (1 Unrelated Failure)

As of commit dd5b83e with merge base d3da92d ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• Apple / upload-frameworks-ios (gh) (detected as infra flaky with no log or failing log classifier)

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[python3kgae]

Tested install_requirements.py under WSL and native Windows only.
Need help to test under Linux and Mac.

[dbort]

This is looking great! Thank you so much for taking the time to do this. It'll be great to reduce the duplication between windows and non-windows.

[dbort]

Thanks for the update! This looks great. I'll try running it locally when I have a chance.

Changes have been made

[dbort]

Worked for me on mac. I updated the PR summary with the steps that I followed. I'm waiting for jobs to finish, but I should be able to merge this soon.

[dbort]

Undid the nightly string change at @lucylq's request; we're not ready to bump it yet.

[dbort]

I just removed the date-changing commit from this PR, going back to a previous state that's already been tested. Merging.

[dbort]

Thank you again for doing this @python3kgae! This is something we've wanted to do for a while, and it really helps cut down on the duplication when making it work for Windows.

[python3kgae]

Thank you again for doing this @python3kgae! This is something we've wanted to do for a while, and it really helps cut down on the duplication when making it work for Windows.

Thank you for the review and testing. We are now closer to achieving a native Windows build.