test: improve assertions in pummel/test-timers

* Timers should not fire early. Check for that.
* Allow the wiggle-room to increase on subsequent iterations of
  intervals.

PR-URL: #35216
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Andrey Pechkurov <apechkurov@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

test/pummel/test-timers.js

@@ -36,7 +36,7 @@ const WINDOW = 200; // Why does this need to be so big?
     assert.ok(diff > 0);
     console.error(`diff: ${diff}`);
 
-    assert.strictEqual(1000 - WINDOW < diff && diff < 1000 + WINDOW, true);
+    assert.ok(1000 <= diff && diff < 1000 + WINDOW);
   }), 1000);
 }
 
@@ -61,7 +61,7 @@ const WINDOW = 200; // Why does this need to be so big?
 
     const t = interval_count * 1000;
 
-    assert.ok(t - WINDOW < diff && diff < t + WINDOW, `t: ${t}`);
+    assert.ok(t <= diff && diff < t + (WINDOW * interval_count));
 
     assert.ok(interval_count <= 3, `interval_count: ${interval_count}`);
     if (interval_count === 3)