test: improve logged errors

To indicate which lines are test lines and which from Node.js core,
it's good to rely on `util.inspect()` while inspecting errors.

The stack was accessed directly instead in multiple cases and logging
that does not provide as much information as using `util.inspect()`.

PR-URL: https://github.com/nodejs/node/pull/31425
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yihong Wang <yh.wang@ibm.com>

test/parallel/test-http-unix-socket.js

@@ -69,7 +69,7 @@ server.listen(common.PIPE, common.mustCall(function() {
   }));
 
   req.on('error', function(e) {
-    assert.fail(e.stack);
+    assert.fail(e);
   });
 
   req.end();