Auto merge of #21933 - notriddle:navigation-redirect-status-code, r=nox

Thread the status through navigation redirects

This is necessary because status codes affect whether the redirect is done with the same HTTP method or a different one.

This is part of #21886, but there's also a flaw in how iframes are handled that is causing the redirect to take over the entire window, so this commit doesn't entirely fix slither.io.

---
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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 are part of #21886, but more changes are needed to actually fix it

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tests/wpt/metadata/MANIFEST.json

@@ -283001,6 +283001,11 @@
      {}
     ]
    ],
+   "fetch/redirect-navigate/302-found-post-handler.py": [
+    [
+     {}
+    ]
+   ],
    "fetch/sec-metadata/README.md": [
     [
      {}
@@ -359258,6 +359263,12 @@
      {}
     ]
    ],
+   "fetch/redirect-navigate/302-found-post.html": [
+    [
+     "/fetch/redirect-navigate/302-found-post.html",
+     {}
+    ]
+   ],
    "fetch/sec-metadata/embed.tentative.https.sub.html": [
     [
      "/fetch/sec-metadata/embed.tentative.https.sub.html",
@@ -601413,6 +601424,14 @@
    "faaee86734e93bb514095e34671a57e00bcbcd98",
    "testharness"
   ],
+  "fetch/redirect-navigate/302-found-post-handler.py": [
+   "23bf4b2c522b7c00ab6bd0fc3eb99f0737d512ec",
+   "support"
+  ],
+  "fetch/redirect-navigate/302-found-post.html": [
+   "854cd329a8f12052bb79f35dd80268f246a52afd",
+   "testharness"
+  ],
   "fetch/sec-metadata/README.md": [
    "c460aa1ecb941118b6999209ba4601eb145a61b9",
    "support"