[3.15] gh-155218: Generate the option group flags in a stable order (GH-155219) (GH-155226)

They were emitted in the iteration order of a set of group identifiers.
The identifiers of the groups before the required parameters are small
negative integers, -1 and -2 have the same hash, so their order depended
on the size of Py_hash_t, and the code generated on a 32-bit platform
differed from the checked in one.

They are now emitted in the order of the parameters.
(cherry picked from commit 7aec160)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: serhiy-storchaka

Misc/NEWS.d/next/Tools-Demos/2026-08-05-14-02-55.gh-issue-155218.Nq4xZv.rst

@@ -0,0 +1,2 @@
+Fix Argument Clinic generating the flags of the optional groups in
+different order on 32-bit and 64-bit platforms.

Modules/clinic/_cursesmodule.c.h

@@ -321,7 +321,9 @@ def render_option_group_parsing(
 """)
                 continue
 
-            group_ids = {p.group for p in subset}  # eliminate duplicates
+            # A set would eliminate duplicates too, but the iteration
+            # order of small negative integers depends on the platform.
+            group_ids = dict.fromkeys(p.group for p in subset)
             d: dict[str, str | int] = {}
             d['count'] = count
             d['name'] = f.name
@@ -332,7 +334,7 @@ def render_option_group_parsing(
                 p.converter.parse_argument(parse_arguments)
             d['parse_arguments'] = ", ".join(parse_arguments)
 
-            group_ids.discard(0)
+            group_ids.pop(0, None)
             lines = "\n".join([
                 self.group_to_variable_name(g) + " = 1;"
                 for g in group_ids