[GR-26084] Flush stdio after interactive REPL statements.

[graalvmbot]

No description provided.

[github-actions]

@steve-s - CI workflow failed: View workflow
Failed tests:

• graalpython/lib-python/3/test/test_multiprocessing_fork::test.test_multiprocessing_fork.test_misc.TestResourceTracker.test_resource_tracker_sigterm
• graalpython/com.oracle.graal.python.test/src/tests/test_subprocess.py::tests.test_subprocess.TestSubprocess.test_graal_python_args
• graalpython/lib-python/3/test/test_datetime.py::test.datetimetester.ZoneInfoTest[America/Tijuana]_Pure.test_system_transitions
• graalpython/lib-python/3/test/test_datetime.py::test.datetimetester.ZoneInfoTest[Europe/Chisinau]_Pure.test_system_transitions
• graalpython/lib-python/3/test/test_datetime.py::test.datetimetester.ZoneInfoTest[America/Tijuana]_Fast.test_system_transitions
• graalpython/lib-python/3/test/test_datetime.py::test.datetimetester.ZoneInfoTest[Europe/Chisinau]_Fast.test_system_transitions
• graalpython/lib-python/3/test/test_asyncio::test.test_asyncio.test_tasks.RunCoroutineThreadsafeTests.test_run_coroutine_threadsafe_task_factory_exception