Auto merge of #18676 - gterzian:continue_http_cache_work, r=jdm

Continue http cache work

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Work in progress, and not quite worth a review yet. (Continuation of https://github.com/servo/servo/pull/4117)

TODO

- [ ] cache metadata (find some subset of`net_traits::Metadata` that can be shared across threads, it seems the problem is mainly stuff inside `hyper::header` in the `headers` field)

- [ ] determine which other fields of a `Response` need to be cached, so a full and valid one can be returned upon a cache hit.

- [ ] determine how to best share the cache across fetch threads (inside HttpState like I tried now?)

- [ ] Spend more time reading the spec and make sure the cache follows it where it matters.

- [ ] Make the current wpt tests pass.

- [ ] More...

---
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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #12972  (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/metadata/fetch/api/basic/accept-header.any.js.ini

@@ -1,17 +0,0 @@
-[accept-header.any.html]
-  type: testharness
-  [Request through fetch should have 'accept' header with value 'custom/*']
-    expected: FAIL
-
-  [Request through fetch should have 'accept-language' header with value 'bzh']
-    expected: FAIL
-
-
-[accept-header.any.worker.html]
-  type: testharness
-  [Request through fetch should have 'accept' header with value 'custom/*']
-    expected: FAIL
-
-  [Request through fetch should have 'accept-language' header with value 'bzh']
-    expected: FAIL
-

tests/wpt/metadata/fetch/api/basic/request-headers.any.js.ini

@@ -39,12 +39,6 @@
   [Fetch with Chicken with body]
     expected: FAIL
 
-  [Fetch with TacO and mode "same-origin" needs an Origin header]
-    expected: FAIL
-
-  [Fetch with TacO and mode "cors" needs an Origin header]
-    expected: FAIL
-
 
 [request-headers.any.worker.html]
   type: testharness