Add package_type field to repodata.json. ### Description

This PR adds `package_type` field to repodata.json and use it to create a list of unvendored standard libraries. After this we don't need to manage a hard-coded list of unvendored stdlib lists in pyodide-py.

### Checklists

- [x] Add / update tests

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name: Documentation improvement
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title: ""
labels: documentation
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## 📚 Documentation

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---
name: Documentation improvement
about: Improve or fix the documentation
title: ""
labels: documentation
assignees: ""
---

## 📚 Documentation

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For typos and doc fixes, please go ahead and:

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