zlib: track memory allocated by zlib

Provide a custom memory allocator for zlib, and track
memory allocated by the library with it.

Right now this “only” makes reported external memory
usage (much) more accurate and protects against zlib
memory leaks, but it generally will enable us to give
more accurate memory usage statistics for zlib.

PR-URL: https://github.com/nodejs/node/pull/21608


Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>