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

import pytest


@pytest.mark.driver_timeout(40)
def test_pyb2d(selenium_standalone, request):
    selenium = selenium_standalone
    selenium.load_package("pyb2d")

    selenium.run(
        """
        import numpy as np
        import b2d
        w = b2d.world(gravity=(0,-10))
        """
    )

import pytest


@pytest.mark.driver_timeout(40)
def test_pyb2d(selenium_standalone, request):
    selenium = selenium_standalone
    selenium.load_package("pyb2d")

    selenium.run(
        """
        import numpy as np
        import b2d
        w = b2d.world(gravity=(0,-10))
        """
    )
