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

package:
  name: scipy
  version: 1.8.0

source:
  url: https://files.pythonhosted.org/packages/b4/a2/4faa34bf0cdbefd5c706625f1234987795f368eb4e97bde9d6f46860843e/scipy-1.8.0.tar.gz
  sha256: 31d4f2d6b724bc9a98e527b5849b8a7e589bf1ea630c33aa563eda912c9ff0bd

requirements:
  run:
    - numpy
    - CLAPACK

test:
  imports:
    - scipy

package:
  name: scipy
  version: 1.8.0

source:
  url: https://files.pythonhosted.org/packages/b4/a2/4faa34bf0cdbefd5c706625f1234987795f368eb4e97bde9d6f46860843e/scipy-1.8.0.tar.gz
  sha256: 31d4f2d6b724bc9a98e527b5849b8a7e589bf1ea630c33aa563eda912c9ff0bd

requirements:
  run:
    - numpy
    - CLAPACK

test:
  imports:
    - scipy
