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: cpp-exceptions-test
  version: "0.1"
  tag:
    - core
    - pyodide.test

source:
  path: src
build:
  type: shared_library
  script: |
    em++ -c throw.cpp -o throw.o ${SIDE_MODULE_CFLAGS} -fexceptions
    em++ -c catch.cpp -o catch.o ${SIDE_MODULE_CFLAGS} -fexceptions
    em++ throw.o ${SIDE_MODULE_LDFLAGS} -o ${DISTDIR}/cpp-exceptions-test-throw.so -fexceptions
    em++ catch.o ${SIDE_MODULE_LDFLAGS} -o ${DISTDIR}/cpp-exceptions-test-catch.so -fexceptions

package:
  name: cpp-exceptions-test
  version: "0.1"
  tag:
    - core
    - pyodide.test

source:
  path: src
build:
  type: shared_library
  script: |
    em++ -c throw.cpp -o throw.o ${SIDE_MODULE_CFLAGS} -fexceptions
    em++ -c catch.cpp -o catch.o ${SIDE_MODULE_CFLAGS} -fexceptions
    em++ throw.o ${SIDE_MODULE_LDFLAGS} -o ${DISTDIR}/cpp-exceptions-test-throw.so -fexceptions
    em++ catch.o ${SIDE_MODULE_LDFLAGS} -o ${DISTDIR}/cpp-exceptions-test-catch.so -fexceptions
