test: better assertion for async hook tests

The existing assertion was misleading to whether there were too few or
too many events of a particular type. Improve the assertion message.

PR-URL: #27601
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/async-hooks/verify-graph.js

@@ -108,7 +108,8 @@ module.exports = function verifyGraph(hooks, graph) {
 
   for (const type in expTypes) {
     assert.strictEqual(typeSeen[type], expTypes[type],
-                       `Expecting type '${type}' in graph`);
+                       `Type '${type}': expecting: ${expTypes[type]} ` +
+                       `found ${typeSeen[type]}`);
   }
 };