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

from pytest_pyodide import run_in_pyodide


@run_in_pyodide(packages=["test", "lzma"], pytest_assert_rewrites=False)
def test_lzma(selenium):
    # TODO: libregrtest.main(["test_lzma"]) doesn't collect any tests for some unknown reason.

    import test.test_lzma
    import unittest

    suite = unittest.TestSuite(
        [unittest.TestLoader().loadTestsFromModule(test.test_lzma)]
    )

    runner = unittest.TextTestRunner(verbosity=2)
    result = runner.run(suite)
    assert result.wasSuccessful()

from pytest_pyodide import run_in_pyodide


@run_in_pyodide(packages=["test", "lzma"], pytest_assert_rewrites=False)
def test_lzma(selenium):
    # TODO: libregrtest.main(["test_lzma"]) doesn't collect any tests for some unknown reason.

    import test.test_lzma
    import unittest

    suite = unittest.TestSuite(
        [unittest.TestLoader().loadTestsFromModule(test.test_lzma)]
    )

    runner = unittest.TextTestRunner(verbosity=2)
    result = runner.run(suite)
    assert result.wasSuccessful()
