Reworked for current Python conventions

[rocky]

• Use pyproject.toml
• Reorganize along current Python project guidelines
• Revise tests for pytest

[rocky]

@mmatera If we are going to get Mathics3 working with Python 3.14, we will need a version of "stopit" (now called Timed-Threads here.)

I would like to put out this package on PyPI.

The reason for not continuing along the lines of stopit is that the purpose of this, as I see it, is pretty limited to Mathics3. So I don't care about any version of Python before what Mathics3 supports.

And we are using basically Mathics3's project conventions: its editorconfig, and its precommit hooks.

At some point, Python will support hardware threads, and then we will be able to support TimedConstrained in a better way, and then this package will disappear.

Although initially I was for working with the stopit author/maintainer, there hadn't been much activity on this. So for expedience, I'd like to just have this be its own thing for what I believe will be the limited time and limited use of this package.

[mmatera]

@rocky , thanks! I agree: at this point it is better to have our own small package than wait for the update ot the other project.

[rocky]

@rocky , thanks! I agree: at this point it is better to have our own small package than wait for the update ot the other project.

Great. I will be putting this on PyPI tomorrow. And then in mathics-core, I'll correct the draft PR.