pythongh-141442: Add escaping to iOS testbed arguments (pythonGH-141443)

Xcode concatenates the test argument array, losing quoting in the process.
(cherry picked from commit 558936b)

Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>

Author: freakboy3742

Misc/NEWS.d/next/Tools-Demos/2025-11-12-12-54-28.gh-issue-141442.50dS3P.rst

@@ -0,0 +1 @@
+The iOS testbed now correctly handles test arguments that contain spaces.

iOS/testbed/__main__.py

@@ -1,6 +1,7 @@
 import argparse
 import json
 import re
+import shlex
 import shutil
 import subprocess
 import sys
@@ -206,7 +207,7 @@ def update_test_plan(testbed_path, args):
         test_plan = json.load(f)
 
     test_plan["defaultOptions"]["commandLineArgumentEntries"] = [
-        {"argument": arg} for arg in args
+        {"argument": shlex.quote(arg)} for arg in args
     ]
 
     with test_plan_path.open("w", encoding="utf-8") as f: