Overturn limitation when releasing deep datastructures involving TripleDicts and other weakrefs

[nthiery]

Deleting TripleDicts and other weakref friends is currently recursive which limits
the depth of datastructures involving them that can be safely deleted. E.g:

from sage.structure.coerce_dict import MonoDict
M = MonoDict(11)

class A: pass
a = A()
prev = a

for i in range(1000):
    newA = A()
    M[prev] = newA
    prev = newA

len(M)
del a
Exception RuntimeError: 'maximum recursion depth exceeded while calling a Python object' in <sage.structure.coerce_dict.MonoDictEraser object at 0x5a13788> ignored

#10963 is apparently putting more stress on our weakref data structure
and triggers such recursion errors. See
#10963 comment:90 and followups for a
discussion.

CC: @vbraun @nbruin @simon-king-jena

Component: memleak

Reviewer: Simon King

Issue created by migration from https://trac.sagemath.org/ticket/15070

[simon-king-jena]

Changed author from Simon King to none

[simon-king-jena]

Reviewer: Simon King

[simon-king-jena]

comment:1

I was faster ;)

This ticket is a duplicate of #15069.