bpo-43687: Py_Initialize() creates singletons earlier (GH-25147)

Reorganize pycore_interp_init() to initialize singletons before the
the first PyType_Ready() call. Fix an issue when Python is configured
using --without-doc-strings.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index f6bf505..74c5888 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -15676,18 +15676,6 @@ PyTypeObject PyUnicode_Type = {
 PyStatus
 _PyUnicode_Init(PyInterpreterState *interp)
 {
-    /* XXX - move this array to unicodectype.c ? */
-    const Py_UCS2 linebreak[] = {
-        0x000A, /* LINE FEED */
-        0x000D, /* CARRIAGE RETURN */
-        0x001C, /* FILE SEPARATOR */
-        0x001D, /* GROUP SEPARATOR */
-        0x001E, /* RECORD SEPARATOR */
-        0x0085, /* NEXT LINE */
-        0x2028, /* LINE SEPARATOR */
-        0x2029, /* PARAGRAPH SEPARATOR */
-    };
-
     struct _Py_unicode_state *state = &interp->unicode;
     if (unicode_create_empty_string_singleton(state) < 0) {
         return _PyStatus_NO_MEMORY();
@@ -15695,23 +15683,39 @@ _PyUnicode_Init(PyInterpreterState *interp)
 
     if (_Py_IsMainInterpreter(interp)) {
         /* initialize the linebreak bloom filter */
+        const Py_UCS2 linebreak[] = {
+            0x000A, /* LINE FEED */
+            0x000D, /* CARRIAGE RETURN */
+            0x001C, /* FILE SEPARATOR */
+            0x001D, /* GROUP SEPARATOR */
+            0x001E, /* RECORD SEPARATOR */
+            0x0085, /* NEXT LINE */
+            0x2028, /* LINE SEPARATOR */
+            0x2029, /* PARAGRAPH SEPARATOR */
+        };
         bloom_linebreak = make_bloom_mask(
             PyUnicode_2BYTE_KIND, linebreak,
             Py_ARRAY_LENGTH(linebreak));
+    }
 
-        if (PyType_Ready(&PyUnicode_Type) < 0) {
-            return _PyStatus_ERR("Can't initialize unicode type");
-        }
+    return _PyStatus_OK();
+}
 
-        if (PyType_Ready(&EncodingMapType) < 0) {
-             return _PyStatus_ERR("Can't initialize encoding map type");
-        }
-        if (PyType_Ready(&PyFieldNameIter_Type) < 0) {
-            return _PyStatus_ERR("Can't initialize field name iterator type");
-        }
-        if (PyType_Ready(&PyFormatterIter_Type) < 0) {
-            return _PyStatus_ERR("Can't initialize formatter iter type");
-        }
+
+PyStatus
+_PyUnicode_InitTypes(void)
+{
+    if (PyType_Ready(&PyUnicode_Type) < 0) {
+        return _PyStatus_ERR("Can't initialize unicode type");
+    }
+    if (PyType_Ready(&EncodingMapType) < 0) {
+         return _PyStatus_ERR("Can't initialize encoding map type");
+    }
+    if (PyType_Ready(&PyFieldNameIter_Type) < 0) {
+        return _PyStatus_ERR("Can't initialize field name iterator type");
+    }
+    if (PyType_Ready(&PyFormatterIter_Type) < 0) {
+        return _PyStatus_ERR("Can't initialize formatter iter type");
     }
     return _PyStatus_OK();
 }