Auto merge of #23323 - nehalem501:master, r=jdm

Implement connectStart in PerformanceResourceTiming

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- Added connectStart where needed (```ResourceFetchTiming```, ```ResourceAttribute```) in ```components/net_traits/lib.rs ```
- Before calling ```client.request``` in ```obtain_response```, we now add the ```connectStart``` attribute (```components/net/http_loader.rs```)
- Updated tests to reflect those changes

---
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- [X] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [X] These changes fix #21261 (at least partially)

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

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components/net/http_loader.rs

@@ -381,6 +381,12 @@ fn obtain_response(
     // TODO(#21261) connect_start: set if a persistent connection is *not* used and the last non-redirected
     // fetch passes the timing allow check
     let connect_start = precise_time_ms();
+    context
+        .timing
+        .lock()
+        .unwrap()
+        .set_attribute(ResourceAttribute::ConnectStart(connect_start));
+
     // https://url.spec.whatwg.org/#percent-encoded-bytes
     let request = HyperRequest::builder()
         .method(method)