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
def test_bz2(selenium):
    import bz2

    text = "Hello test test test test this is a test test test"
    some_compressed_bytes = bz2.compress(text.encode("utf-8"))
    assert some_compressed_bytes != text.encode("utf-8")
    decompressed_bytes = bz2.decompress(some_compressed_bytes)
    assert decompressed_bytes.decode("utf-8") == text

from pytest_pyodide import run_in_pyodide


@run_in_pyodide
def test_bz2(selenium):
    import bz2

    text = "Hello test test test test this is a test test test"
    some_compressed_bytes = bz2.compress(text.encode("utf-8"))
    assert some_compressed_bytes != text.encode("utf-8")
    decompressed_bytes = bz2.decompress(some_compressed_bytes)
    assert decompressed_bytes.decode("utf-8") == text
