gh-114058: Fix flaky globals to constant test

[Fidget-Spinner]

The optimizer does not optimize global loads if the builtins dictionary has been modified more than 3 times. In this case, I suspect some other test is modifying the builtins dictionary before test_capi.test_opt is run. So the test for the optimizer fails if tests are run sequentially.

The solution is to run the test in the subprocess so it's not subject to shenanigans that other tests do :).

• Issue: Tier 2 optimizer's abstract interpreter #114058

[Fidget-Spinner]

Easy reproducer: thanks to @Eclips4

./python -m test test___all__ test__locale test__opcode test__osx_support test__xxinterpchannels test__xxsubinterpreters test_abc test_abstract_numbers test_argparse test_array test_asdl_parser test_ast test_asyncgen test_atexit test_audit test_augassign test_augassign test_baseexception test_bdb test_bigaddrspace test_bigmem test_binascii test_binop test_bisect test_bool test_buffer test_bufio test_builtin test_bytes test_bz2 test_c_locale_coercion test_calendar test_call test_capi 

[Eclips4]

Easy reproducer: thanks to @Eclips4

./python -m test test___all__ test__locale test__opcode test__osx_support test__xxinterpchannels test__xxsubinterpreters test_abc test_abstract_numbers test_argparse test_array test_asdl_parser test_ast test_asyncgen test_atexit test_audit test_augassign test_augassign test_baseexception test_bdb test_bigaddrspace test_bigmem test_binascii test_binop test_bisect test_bool test_buffer test_bufio test_builtin test_bytes test_bz2 test_c_locale_coercion test_calendar test_call test_capi 

I found the more easier reproducer:

./python -m test test_argparse test_ast test_asyncgen test_capi 

[Eclips4]

macOS failure is unrelated, see #115383 for more information