Merge pyodide_py into python_stdlib.zip. ### Description

Merges pyodide_py.tar into python_stdlib.zip. This reduces the number of network requests during the initialization.

The original intention of splitting pyodide_py.tar from pyodide.asm.data was to give users an option to provide custom files (#2023), which is now available by modifying python_stdlib.zip directly. So I think there is no reason to have both python_stdlib.zip and pyodide_py.tar.

### Checklists

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests

from pytest_pyodide import run_in_pyodide


@run_in_pyodide(packages=["fpcast-test"])
def test_fpcasts(selenium):
    import fpcast_test

    fpcast_test.noargs0()
    fpcast_test.noargs1()
    fpcast_test.noargs2()
    fpcast_test.noargs3()

    fpcast_test.varargs0()
    fpcast_test.varargs1()
    fpcast_test.varargs2()
    fpcast_test.varargs3()

    fpcast_test.kwargs0()
    fpcast_test.kwargs1()
    fpcast_test.kwargs2()
    fpcast_test.kwargs3()

    fpcast_test.Callable0()()
    fpcast_test.Callable1()()
    fpcast_test.Callable2()()
    fpcast_test.Callable3()()

    t = fpcast_test.TestType()
    t.noargs0()
    t.noargs1()
    t.noargs2()
    t.noargs3()

    t.varargs0()
    t.varargs1()
    t.varargs2()
    t.varargs3()

    t.kwargs0()
    t.kwargs1()
    t.kwargs2()
    t.kwargs3()

    t.getset0
    t.getset1
    t.getset1 = 5

from pytest_pyodide import run_in_pyodide


@run_in_pyodide(packages=["fpcast-test"])
def test_fpcasts(selenium):
    import fpcast_test

    fpcast_test.noargs0()
    fpcast_test.noargs1()
    fpcast_test.noargs2()
    fpcast_test.noargs3()

    fpcast_test.varargs0()
    fpcast_test.varargs1()
    fpcast_test.varargs2()
    fpcast_test.varargs3()

    fpcast_test.kwargs0()
    fpcast_test.kwargs1()
    fpcast_test.kwargs2()
    fpcast_test.kwargs3()

    fpcast_test.Callable0()()
    fpcast_test.Callable1()()
    fpcast_test.Callable2()()
    fpcast_test.Callable3()()

    t = fpcast_test.TestType()
    t.noargs0()
    t.noargs1()
    t.noargs2()
    t.noargs3()

    t.varargs0()
    t.varargs1()
    t.varargs2()
    t.varargs3()

    t.kwargs0()
    t.kwargs1()
    t.kwargs2()
    t.kwargs3()

    t.getset0
    t.getset1
    t.getset1 = 5
