bpo-46608: exclude marshalled-frozen data if deep-freezing to save 300 KB space (GH-31074)

This reduces the size of the data segment by **300 KB** of the executable because if the modules are deep-frozen then the marshalled frozen data just wastes space. This was inspired by comment by @gvanrossum in https://github.com/python/cpython/pull/29118#issuecomment-958521863. Note: There is a new option `--deepfreeze-only` in `freeze_modules.py` to change this behavior, it is on be default to save disk space.
```console 
# du -s ./python before
27892   ./python
# du -s ./python after
27524   ./python
```

Automerge-Triggered-By: GH:ericsnowcurrently

1 files changed, 12 insertions, 4 deletions

diff --git a/Python/import.c b/Python/import.c
index 51b779c..be60c43 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1297,13 +1297,21 @@ find_frozen(PyObject *nameobj, struct frozen_info *info)
         info->nameobj = nameobj;  // borrowed
         info->data = (const char *)p->code;
         info->get_code = p->get_code;
-        info->size = p->size < 0 ? -(p->size) : p->size;
-        info->is_package = p->size < 0 ? true : false;
+        info->size = p->size;
+        info->is_package = p->is_package;
+        if (p->size < 0) {
+            // backward compatibility with negative size values
+            info->size = -(p->size);
+            info->is_package = true;
+        }
         info->origname = name;
         info->is_alias = resolve_module_alias(name, _PyImport_FrozenAliases,
                                               &info->origname);
     }
-
+    if (p->code == NULL && p->size == 0 && p->get_code != NULL) {
+        /* It is only deepfrozen. */
+        return FROZEN_OKAY;
+    }
     if (p->code == NULL) {
         /* It is frozen but marked as un-importable. */
         return FROZEN_EXCLUDED;
@@ -2224,7 +2232,7 @@ _imp_get_frozen_object_impl(PyObject *module, PyObject *name,
     if (info.nameobj == NULL) {
         info.nameobj = name;
     }
-    if (info.size == 0) {
+    if (info.size == 0 && info.get_code == NULL) {
         /* Does not contain executable code. */
         set_frozen_error(FROZEN_INVALID, name);
         return NULL;