gh-101758: Clean Up Uses of Import State (gh-101919)

This change is almost entirely moving code around and hiding import state behind internal API.  We introduce no changes to behavior, nor to non-internal API.  (Since there was already going to be a lot of churn, I took this as an opportunity to re-organize import.c into topically-grouped sections of code.)  The motivation is to simplify a number of upcoming changes.

Specific changes:

* move existing import-related code to import.c, wherever possible
* add internal API for interacting with import state (both global and per-interpreter)
* use only API outside of import.c (to limit churn there when changing the location, etc.)
* consolidate the import-related state of PyInterpreterState into a single struct field (this changes layout slightly)
* add macros for import state in import.c (to simplify changing the location)
* group code in import.c into sections
*remove _PyState_AddModule()

https://github.com/python/cpython/issues/101758

1 files changed, 2 insertions, 8 deletions

diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 6a4d593768..ce993ea879 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -350,14 +350,8 @@ static int
 set_main_loader(PyObject *d, PyObject *filename, const char *loader_name)
 {
     PyInterpreterState *interp = _PyInterpreterState_GET();
-    PyObject *bootstrap = PyObject_GetAttrString(interp->importlib,
-                                                 "_bootstrap_external");
-    if (bootstrap == NULL) {
-        return -1;
-    }
-
-    PyObject *loader_type = PyObject_GetAttrString(bootstrap, loader_name);
-    Py_DECREF(bootstrap);
+    PyObject *loader_type = _PyImport_GetImportlibExternalLoader(interp,
+                                                                 loader_name);
     if (loader_type == NULL) {
         return -1;
     }