ENH Add micropip.search() API

[ryanking13]

🚀 Feature

It would be great to have micropip.search(), analogous to pip search which can search Python packages.

Additional context

micropip.search() can be used before running micropip.install() so that users can search whether:

• The package has a pure Python wheel or not
• The package is a Pyodide package or a PyPI package.

Example output

>>> await micropip.search("numpy")
{"name": "numpy", "version": "1.21.4", "type": "pyodide": "available": True}
>>> await micropip.search("black")
{"name": "black", "version": "22.3.0", "type": "PyPI": "available": True}
>>> await micropip.search("torch")
{"name": "torch", "version": "1.11.0", "type": "PyPI": "available": False}

[rth]

The pip search currently doesn't work pypa/pip#5216 and the corresponding PyPI API is currently disabled https://status.python.org/incidents/grk0k7sz6zkp. For now the only working solutions is https://github.com/victorgarric/pip_search as far as I know.

Though in the end since since users seem to be doing fine without this functionality in pip, maybe there could also live without it in micropip.