test: log before and after RSS in memory leak test

Refs: https://github.com/nodejs/node/issues/21076

PR-URL: https://github.com/nodejs/node/pull/21080
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-crypto-dh-leak.js

@@ -23,4 +23,4 @@ const after = process.memoryUsage().rss;
 
 // RSS should stay the same, ceteris paribus, but allow for
 // some slop because V8 mallocs memory during execution.
-assert(after - before < 5 << 20);
+assert(after - before < 5 << 20, `before=${before} after=${after}`);