gh-108416: Mark slow test methods with @requires_resource('cpu') (GH-108421)

Only mark tests which spend significant system or user time,
by itself or in subprocesses.

Lib/test/test_tools/test_freeze.py

@@ -17,10 +17,8 @@ with imports_under_tool('freeze', 'test'):
 @support.skip_if_buildbot('not all buildbots have enough space')
 class TestFreeze(unittest.TestCase):
 
+    @support.requires_resource('cpu') # Building Python is slow
     def test_freeze_simple_script(self):
-        # Building Python is slow
-        support.requires('cpu')
-
         script = textwrap.dedent("""
             import sys
             print('running...')