Issue #19512: Add PyRun_InteractiveOneObject() function

Only decode the filename once. PyRun_InteractiveOneObject() uses an identifier
for "<string>" string, so the byte string is only decoded once.
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index ec0565e..c364947 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -63,6 +63,10 @@
     FILE *fp,
     const char *filename,       /* decoded from the filesystem encoding */
     PyCompilerFlags *flags);
+PyAPI_FUNC(int) PyRun_InteractiveOneObject(
+    FILE *fp,
+    PyObject *filename,
+    PyCompilerFlags *flags);
 PyAPI_FUNC(int) PyRun_InteractiveLoopFlags(
     FILE *fp,
     const char *filename,       /* decoded from the filesystem encoding */