gh-133143: Use _Py_ID for the other literals in sys (GH-138698)

Follow-up refactoring after GH-133143, where we use `_Py_ID` for "big" and "little"
in `abi_info.byteorder`.
This uses `_Py_ID` for `sys.byteorder`, but also `float_repr_style` and a module name.

Author: encukou

Include/internal/pycore_global_objects_fini_generated.h

@@ -571,6 +571,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(last_value)
         STRUCT_FOR_ID(latin1)
         STRUCT_FOR_ID(leaf_size)
+        STRUCT_FOR_ID(legacy)
         STRUCT_FOR_ID(len)
         STRUCT_FOR_ID(length)
         STRUCT_FOR_ID(level)
@@ -744,6 +745,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(setstate)
         STRUCT_FOR_ID(shape)
         STRUCT_FOR_ID(shared)
+        STRUCT_FOR_ID(short)
         STRUCT_FOR_ID(show_cmd)
         STRUCT_FOR_ID(signed)
         STRUCT_FOR_ID(signum)

Include/internal/pycore_global_strings.h

@@ -610,7 +610,7 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
 
     if (last_dot == NULL) {
         /* The breakpoint is a built-in, e.g. PYTHONBREAKPOINT=int */
-        modulepath = PyUnicode_FromString("builtins");
+        modulepath = &_Py_ID(builtins);
         attrname = envar;
     }
     else if (last_dot != envar) {
@@ -3873,9 +3873,9 @@ _PySys_InitCore(PyThreadState *tstate, PyObject *sysdict)
     SET_SYS("builtin_module_names", list_builtin_module_names());
     SET_SYS("stdlib_module_names", list_stdlib_module_names());
 #if PY_BIG_ENDIAN
-    SET_SYS_FROM_STRING("byteorder", "big");
+    SET_SYS("byteorder", &_Py_ID(big));
 #else
-    SET_SYS_FROM_STRING("byteorder", "little");
+    SET_SYS("byteorder", &_Py_ID(little));
 #endif
 
 #ifdef MS_COREDLL
@@ -3917,9 +3917,9 @@ _PySys_InitCore(PyThreadState *tstate, PyObject *sysdict)
 
     /* float repr style: 0.03 (short) vs 0.029999999999999999 (legacy) */
 #if _PY_SHORT_FLOAT_REPR == 1
-    SET_SYS_FROM_STRING("float_repr_style", "short");
+    SET_SYS("float_repr_style", &_Py_ID(short));
 #else
-    SET_SYS_FROM_STRING("float_repr_style", "legacy");
+    SET_SYS("float_repr_style", &_Py_ID(legacy));
 #endif
 
     SET_SYS("thread_info", PyThread_GetInfo());