pyodide-lock.json with absolute URLs

[rth]

Suppose we have the tooling to easily generate custom pyodide-lock.json once #3573 is addressed.

A common use case is that one would want to add some packages located on PyPI (or elsewhere) there so that they are loaded on import. Otherwise for instance, if you run existing notebooks in JupyterLite, some packages will be loaded on import, while others need to be pip installed, which is confusing for users, particularly when teaching.

In that scenario, one would want to directly put URLs to PyPI in pyodide-lock.json under the file_name field for some packages. However, I believe currently this would fail to properly work in Node here,

> nodePath.resolve("https://cdn.jsdelivr.net/pyodide/v0.23.3/full" || ".", "https://some-other-url")
'/home/rth/src/pyodide-utils/https:/cdn.jsdelivr.net/pyodide/v0.23.3/full/https:/some-other-url'

while it should be OK in the browser. In any case, we probably need more tests for this use case.