[3.14] gh-135443: Sometimes Fall Back to __main__.__dict__ For Globals (gh-135593)

For several builtin functions, we now fall back to __main__.__dict__ for the globals
when there is no current frame and _PyInterpreterState_IsRunningMain() returns
true.  This allows those functions to be run with Interpreter.call().

The affected builtins:

* exec()
* eval()
* globals()
* locals()
* vars()
* dir()

We take a similar approach with "stateless" functions, which don't use any
global variables.

(cherry picked from commit a450a0ddec, AKA gh-135491)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>

Python/import.c

@@ -3958,25 +3958,28 @@ PyImport_Import(PyObject *module_name)
     }
 
     /* Get the builtins from current globals */
-    globals = PyEval_GetGlobals();
+    globals = PyEval_GetGlobals();  // borrowed
     if (globals != NULL) {
         Py_INCREF(globals);
+        // XXX Use _PyEval_EnsureBuiltins()?
         builtins = PyObject_GetItem(globals, &_Py_ID(__builtins__));
         if (builtins == NULL) {
             // XXX Fall back to interp->builtins or sys.modules['builtins']?
             goto err;
         }
     }
+    else if (_PyErr_Occurred(tstate)) {
+        goto err;
+    }
     else {
         /* No globals -- use standard builtins, and fake globals */
-        builtins = PyImport_ImportModuleLevel("builtins",
-                                              NULL, NULL, NULL, 0);
-        if (builtins == NULL) {
+        globals = PyDict_New();
+        if (globals == NULL) {
             goto err;
         }
-        globals = Py_BuildValue("{OO}", &_Py_ID(__builtins__), builtins);
-        if (globals == NULL)
+        if (_PyEval_EnsureBuiltinsWithModule(tstate, globals, &builtins) < 0) {
             goto err;
+        }
     }
 
     /* Get the __import__ function from the builtins */