src: skip weak references for memory tracking

The memory tracking is supposed to represent the “keeps-alive”
relations between objects for a heap dump, in order to enable
developers to figure out which objects keep which other objects
on the heap.

Weak references do not participate in that relation. Therefore,
we should not be tracking them.

PR-URL: https://github.com/nodejs/node/pull/34469


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>