Do not rely on pip for installing pip packages

[martinRenou]

Problem

pip is broken when it comes to installing things in an emscripten env

Proposed Solution

We should use a similar approach as done in https://github.com/emscripten-forge/mambajs/blob/main/src/solverpip.ts

It would be simple Python scripting requesting package info from PyPi through simple fetches. That's enough to get things done properly without relying on pip.