Get rid of getmem.py helper

Platforms provide an interface for retrieving this information.  Just use
those interfaces instead.

misc/operations_helpers/getmem.py

@@ -1,20 +0,0 @@
-#! /usr/bin/env python
-
-from __future__ import print_function
-
-from foolscap import Tub
-from foolscap.eventual import eventually
-import sys
-from twisted.internet import reactor
-
-def go():
-    t = Tub()
-    d = t.getReference(sys.argv[1])
-    d.addCallback(lambda rref: rref.callRemote("get_memory_usage"))
-    def _got(res):
-        print(res)
-        reactor.stop()
-    d.addCallback(_got)
-
-eventually(go)
-reactor.run()