bpo-39489: Remove COUNT_ALLOCS special build (GH-18259)

Remove:

* COUNT_ALLOCS macro
* sys.getcounts() function
* SHOW_ALLOC_COUNT code in listobject.c
* SHOW_TRACK_COUNT code in tupleobject.c
* PyConfig.show_alloc_count field
* -X showalloccount command line option
* @test.support.requires_type_collecting decorator

Lib/subprocess.py

@@ -325,7 +325,7 @@ def _args_from_interpreter_flags():
     if dev_mode:
         args.extend(('-X', 'dev'))
     for opt in ('faulthandler', 'tracemalloc', 'importtime',
-                'showalloccount', 'showrefcount', 'utf8'):
+                'showrefcount', 'utf8'):
         if opt in xoptions:
             value = xoptions[opt]
             if value is True: