allow micropip to install pyodide wheels

[reynoldsnlp]

Currently, briefcase tries to load compiled wheels from the host platform, which leads to errors when loading in the browser. This PR parses the whl filename and any wheels that are not pure python or wasm32 are replaced with simply the package name, so that micropip can install it. We do not attempt to bundle the whl file compiled for the host platform.

In the future, when Pyodide starts hosting an index, we should download the pyodide wheel and bundle that wheel.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

I think this may be related:

• Web / Add Support for "Pyodide Packages" #1104

[reynoldsnlp]

@rmartin16 Yes, #1104 and #1227 should both be linked to this PR so they close upon merge.

[freakboy3742]

I can see what you're doing here, and it's clever... a little bit too clever :-) We're downloading a platform wheel, then using the existence of a platform wheel to determine whether the wheel reference should be ignored. This will work, but it's going to result in a lot of unused files in the static folder; and potentially inconsistencies in package versions (since the version request in the requires list will be ignored in the resolution to pyscript).

I think I'd prefer to see this addressed at the original installation phase, rather than the "use" phase. In the simplest approach, the list of packages published by Pyodide is known, so we can filter what is pip installed (and that what wheels exist on disk); alternatively, we can potentially self-host copies of the pyodide wheels on a private index; better still would be to convince Pyodide to publish a simple index of their packages.