Bug 1735600 [wpt PR 31216] - [Legacy client hints modernization] (5) Check for `sec...

Bug 1735600 [wpt PR 31216] - [Legacy client hints modernization] (5) Check for `sec-ch-` in WebTests, a=testonly

Automatic update from web-platform-tests
[Legacy client hints modernization] (5) Check for `sec-ch-` in WebTests

This CL adds WebTests for the new names (with the `sec-ch-` prefix) of
the `dpr`, `device-memory`, `width`, and `viewport-width` client hints.

Intent: https://groups.google.com/a/chromium.org/g/blink-dev/c/Y42bZ66L6Zo/

This series of CLs seeks to add `sec-ch-` prefixes to client hints that
are missing them by deprecating the old versions and adding new ones:
(1) Add `sec-ch-` hint constants
(2) Add feature to gate legacy hints for future deprecation
(3) Implement `sec-ch-` device-memory, dpr, width, and viewport-width
(4) Enable `sec-ch-` client hints by default
(5) Check for `sec-ch-` in WebTests
(6) Add deprecation issue for legacy hints

Bug: 1227043
Change-Id: I3065ac322ba2b99426b81942c13fb8014c1ece58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3221278
Auto-Submit: Ari Chivukula <arichiv@chromium.org>
Commit-Queue: Ari Chivukula <arichiv@chromium.org>
Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Cr-Commit-Position: refs/heads/main@{#934051}

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wpt-commits: 2eb218c99de3302dff12a80c92fa7cbca4fcd27f
wpt-pr: 31216