bpo-46471: Use single byte singletons (GH-30781)

Author: kumaraditya303

Misc/NEWS.d/next/Build/2022-01-22-11-06-23.bpo-46471.03snrE.rst

@@ -0,0 +1 @@
+Use global singletons for single byte bytes objects in deepfreeze.

Tools/scripts/deepfreeze.py

@@ -150,6 +150,8 @@ def field(self, obj: object, name: str) -> None:
     def generate_bytes(self, name: str, b: bytes) -> str:
         if b == b"":
             return "(PyObject *)&_Py_SINGLETON(bytes_empty)"
+        if len(b) == 1:
+            return f"(PyObject *)&_Py_SINGLETON(bytes_characters[{b[0]}])"
         self.write("static")
         with self.indent():
             with self.block("struct"):