zlib: be strict about what strategies are accepted

Currently, strategy constants are integers but Node.js will accept
string versions of those integers. Users should be using the provided
zlib constants and not hardcoding numbers, strings, or anything else. As
such, Node.js should be strict about accepting only exactly those values
that are in the provided zlib constants.

PR-URL: https://github.com/nodejs/node/pull/10934
Fixes: https://github.com/nodejs/node/issues/10932


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>