profiling: revert the default mode back to 'cpu' on Windows

On Windows, os.times() only returns user and system times.  Real elapsed time is
0.  That results in no actual times reported, an end wall time of 0.000000, and
seemingly randomly sorted stack frames.  This at least provides test stability
in test-profile.t.

I kind of think that `default=pycompat.iswindows and 'cpu' or 'real'` would be a
better way to set the default in configitems, but I didn't see any other
examples of this, and thought maybe there's a reason for that.  That might allow
plugging the value into the help text automatically- the documented default
wasn't updated in db0dba2d157d.

mercurial/configitems.py

@@ -923,7 +923,7 b" coreconfigitem('profiling', 'statformat'"
     default='hotpath',
 )
 coreconfigitem('profiling', 'time-track',
-    default='real',
+    default=dynamicdefault,
 )
 coreconfigitem('profiling', 'type',
     default='stat',

mercurial/profiling.py

@@ -101,7 +101,8 b' def statprofile(ui, fp):'
     else:
         ui.warn(_("invalid sampling frequency '%s' - ignoring\n") % freq)
 
-    track = ui.config('profiling', 'time-track')
+    track = ui.config('profiling', 'time-track',
+                      pycompat.iswindows and 'cpu' or 'real')
     statprof.start(mechanism='thread', track=track)
 
     try: