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

# setup: from decimal import Decimal ; A = [Decimal('2.1') for i in range(1000)] ; B = [Decimal('3.2') for i in range(1000)]
# run: large_decimal_list(A, B)


def large_decimal_list(A, B):
    return [a * b for a, b in zip(A, B)]

# setup: from decimal import Decimal ; A = [Decimal('2.1') for i in range(1000)] ; B = [Decimal('3.2') for i in range(1000)]
# run: large_decimal_list(A, B)


def large_decimal_list(A, B):
    return [a * b for a, b in zip(A, B)]
