sim,python: follow the new CPython startup sequence

Currently, gem5 suffers from several bugs related
to Python interpreter's locale encoding issues.
gem5 will crash when the working directory contains
Non-ASCII characters.

The reason is that Python 3.8+ introduces a new
interpreter startup sequence [1]. The startup
sequence consists of three phases:

1. Python core runtime preinitialization
2. Python core runtime initialization
3. Main interpreter configuration

Stage 1 determining the encodings used for system
interfaces.

However, gem5 doesn't preinitialize the Python
interpreter. Thus, the locale settings do not take
effect. This patch preinitialize the Python for
Python 3.8+.

Also, this patch avoid the use of `Py_SetProgramName`,
which is deprecated since Python 3.11[3].

[1] https://peps.python.org/pep-0432/
[2] https://peps.python.org/pep-0587/
[3] https://docs.python.org/3/c-api/init.html#c.Py_SetProgramName

Change-Id: I08a2ec6ab2b39a95ab194909932c8fc578c745ce
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/70898
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Roger Chang <rogerycchang@google.com>

src/python/gem5py.cc

@@ -51,6 +51,21 @@ namespace py = pybind11;
 int
 main(int argc, const char **argv)
 {
+#if PY_VERSION_HEX >= 0x03080000
+    // Preinitialize Python for Python 3.8+
+    // This ensures that the locale configuration takes effect
+    PyStatus status;
+    PyPreConfig preconfig;
+    PyPreConfig_InitPythonConfig(&preconfig);
+
+    preconfig.utf8_mode = 1;
+
+    status = Py_PreInitialize(&preconfig);
+    if (PyStatus_Exception(status)) {
+        Py_ExitStatusException(status);
+    }
+#endif
+
     py::scoped_interpreter guard;
 
     // Embedded python doesn't set up sys.argv, so we'll do that ourselves.