Auto merge of #21388 - gterzian:introduce_task_queues, r=jdm

Introduce task queues, and throttling performance timeline tasksource

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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #19997 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -20674,6 +20674,16 @@
      {}
     ]
    ],
+   "mozilla/task_queue_throttling.any.js": [
+    [
+     "/_mozilla/mozilla/task_queue_throttling.any.html",
+     {}
+    ],
+    [
+     "/_mozilla/mozilla/task_queue_throttling.any.worker.html",
+     {}
+    ]
+   ],
    "mozilla/textcontent.html": [
     [
      "/_mozilla/mozilla/textcontent.html",
@@ -32667,6 +32677,10 @@
    "321132b7e7e21d542ce86e4322db04aba3e9d11e",
    "support"
   ],
+  "mozilla/task_queue_throttling.any.js": [
+   "bbf464f384d55a44db6948d6cc7ab5f54509b800",
+   "testharness"
+  ],
   "mozilla/test.jpg": [
    "110b3d6b666d35a117ca8c8ada32bf1002943044",
    "support"