feat(fetch): implement APIResponse.timing()

[dgozman]

Summary

• Expose per-phase resource timing on APIResponse via a new timing() method, mirroring Request.timing(). The timings were already collected for HAR/trace recording; this surfaces them through the public API.
• The return type is shared with Request.timing() in the docs via a new resource-timing template; while sharing, fixed copy-paste errors in domainLookupEnd and connectEnd descriptions.
• Phases that did not happen (e.g. reused keep-alive socket) or are unknown (HAR replay) are reported as -1, consistent with browser requests.

Fixes #41747

[github-actions]

Hi, I'm the Playwright bot and I took a first look at the CI failures.

🟢 Both failures are pre-existing MCP flakes — this PR is clear

This PR only touches APIResponse.timing() (client/server fetch.ts, protocol, and fetch/HAR tests). The two failures are in the MCP annotate flow, which this change doesn't exercise, and both flip verdict across many unrelated PRs.

Details

Pre-existing flake / infra

• [chromium] › mcp/annotate.spec.ts:447 › should switch screencast to -s session on show --annotate — flaky across the test-results DB: failed 7 of 211 chromium runs (~3%) and passed the other 204, over 5 distinct PRs, on SHAs unrelated to this branch. Not caused by this PR.
• [webkit] › mcp/annotate.spec.ts:173 › user-initiated annotate downloads zip with feedback.md — same story: failed 7 of 213 webkit runs (~3%), passed 206, over 3 distinct PRs. This test flakes more heavily on firefox (12/208) too. Not caused by this PR.

Nothing in the diff reaches the MCP annotate/screencast code paths, and the aggregated history shows both tests failing on PRs that predate and are unrelated to this one — so these are flakes, not regressions.

_{Triaged by the Playwright bot - agent run}

[github-actions]

Test results for "MCP"

7760 passed, 1249 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

3 flaky

⚠️ [chromium-library] › library/video.spec.ts:736 › screencast › should work with video+trace `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/video.spec.ts:495 › screencast › should capture static page in persistent context @smoke `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:699 › screencast › should capture full viewport on hidpi `@chromium-ubuntu-22.04-node22`

49716 passed, 1156 skipped

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Merge workflow run.