Add a local PyPI server

[zanieb]

Following support for other package indices (#34) we add support for serving a local package index powered by devpi!

❯ packse index up --bg
Starting server at http://localhost:3141...
Configuring client...
Creating package index 'packages/all'...
Index available at http://localhost:3141/packages/all
Ready!
Running in background with PID 29226
Stop server with `packse index down`.
http://localhost:3141/packages/all

❯ packse publish dist/example-0611cb74 --index-url http://127.0.0.1:3141/packages/all --anonymous
Publishing 1 target to http://127.0.0.1:3141/packages/all...
Publishing 'example-0611cb74'...
Published 'example_0611cb74-0.0.0.tar.gz'
Published 'example_0611cb74_a-1.0.0-py3-none-any.whl'
Published 'example_0611cb74_a-1.0.0.tar.gz'
Published 'example_0611cb74_b-1.0.0-py3-none-any.whl'
Published 'example_0611cb74_b-1.0.0.tar.gz'
example-0611cb74

❯ pip install --index-url http://127.0.0.1:3141/packages/all example-0611cb74 -q
❯ python -c "import example_0611cb74; print(example_0611cb74.__version__)"
0.0.0

❯ packse index down
Stopping server at PID 29226...
Stopped server!

I plan to add support for passing scenarios directly to a packse serve command which will build and publish them.

The index is backed by PyPI so if you need a package that is not in the scenario it will get downloaded.

The server runs backed by a temporary directory if not in the background, but a background server requires a persistent directory in ~/.packse.

To support true offline indices, we need to mirror hatchling.