configitems: register the 'profiling.output' config

mercurial/configitems.py

@@ -335,6 +335,9 b" coreconfigitem('profiling', 'limit',"
 coreconfigitem('profiling', 'nested',
     default=0,
 )
+coreconfigitem('profiling', 'output',
+    default=None,
+)
 coreconfigitem('profiling', 'sort',
     default='inlinetime',
 )