This is meant to address Issue 14766.

* DEP: remove allocation_tracking

* DOC: add release note

* DEP: deprecate PyDataMem_SetEventHook

* DOC: fix name of release note

* fixes from review

* DOC: document deprecation of PyDataMem_EventHookFunc

Inheriting from object was necessary for Python 2 compatibility to use
new-style classes. In Python 3, this is unnecessary as there are no
old-style classes.

Dropping the object is more idiomatic Python.

As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.

Bare except is very rarely the right thing

Python 3.6 added a private API for tracing arbitrary memory allocations
so the tracemalloc module [0] can be used with numpy.

closes gh-4663

[0] https://docs.python.org/3/library/tracemalloc.html

When a cython object contains numpy arrays the pure python allocation
hook can trigger during cythons __dealloc__ method and trigger a second
deletion of the object currently being deleted.
To minimize the probabily that that happens disable the garbage
collector during the hook.
As this involves python calls it is still possible that a double delete
occurs but chances are lowered, a proper solution would be C only hook
like python 3.4 tracemalloc module.

Closes gh-4834