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

package:
  name: cycler
  version: 0.11.0
  top-level:
    - cycler
source:
  url: https://files.pythonhosted.org/packages/5c/f9/695d6bedebd747e5eb0fe8fad57b72fdf25411273a39791cde838d5a8f51/cycler-0.11.0-py3-none-any.whl
  sha256: 3a27e95f763a428a739d2add979fa7494c912a32c17c4c38c4d5f082cad165a3
requirements:
  run:
    - six
about:
  home: https://github.com/matplotlib/cycler
  PyPI: https://pypi.org/project/cycler
  summary: Composable style cycles
  license: BSD

package:
  name: cycler
  version: 0.11.0
  top-level:
    - cycler
source:
  url: https://files.pythonhosted.org/packages/5c/f9/695d6bedebd747e5eb0fe8fad57b72fdf25411273a39791cde838d5a8f51/cycler-0.11.0-py3-none-any.whl
  sha256: 3a27e95f763a428a739d2add979fa7494c912a32c17c4c38c4d5f082cad165a3
requirements:
  run:
    - six
about:
  home: https://github.com/matplotlib/cycler
  PyPI: https://pypi.org/project/cycler
  summary: Composable style cycles
  license: BSD
