gh-103875: Use ascii and latin1 singletons in deepfreeze (#103876)

Author: oraluben

Tools/build/deepfreeze.py

@@ -175,6 +175,12 @@ def generate_unicode(self, name: str, s: str) -> str:
             return f"&_Py_STR({strings[s]})"
         if s in identifiers:
             return f"&_Py_ID({s})"
+        if len(s) == 1:
+            c = ord(s)
+            if c < 128:
+                return f"(PyObject *)&_Py_SINGLETON(strings).ascii[{c}]"
+            elif c < 256:
+                return f"(PyObject *)&_Py_SINGLETON(strings).latin1[{c - 128}]"
         if re.match(r'\A[A-Za-z0-9_]+\Z', s):
             name = f"const_str_{s}"
         kind, ascii = analyze_character_width(s)