Auto merge of #23178 - tdelacour:ISSUE-21263, r=jdm

Add PerformanceResourceTiming: ResponseEnd

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1. Added `ResponseEnd` to `ResourceAttribute` enum in `net_traits` and added it to the `set_attribute` function on `ResourceFetchTiming`
2. Added `response_end` field to `performanceresourcetiming.rs`
3. In `http_loader.rs`, set ResponseEnd after response body read is complete, or before return due to network error.

I could use a little guidance on testing. After building and running `wpt` tests, I noticed that some tests now "Pass" when they were expected to "Fail". As per the wiki instructions, I've removed those expectations from the `metadata`.

I noticed that there are a handful of other "failing" test expectations associated with `responseEnd`, but those still do not pass. I looked through some similar PRs (`connectEnd`, `redirectStart`, etc) and saw that they also still have a few failing test expectations here and there. Does that mean this is OK for now? How can I better understand which tests we expect to resolve for a given issue? Thanks!

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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 #21263 (GitHub issue number if applicable)

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

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