GH-96421: Insert shim frame on entry to interpreter (GH-96319)

* Adds EXIT_INTERPRETER instruction to exit PyEval_EvalDefault()

* Simplifies RETURN_VALUE, YIELD_VALUE and RETURN_GENERATOR instructions as they no longer need to check for entry frames.

Include/internal/pycore_global_strings.h

@@ -48,6 +48,7 @@ struct _Py_global_strings {
         STRUCT_FOR_STR(newline, "\n")
         STRUCT_FOR_STR(open_br, "{")
         STRUCT_FOR_STR(percent, "%")
+        STRUCT_FOR_STR(shim_name, "<shim>")
         STRUCT_FOR_STR(utf_8, "utf-8")
     } literals;