Bug 1764967 [wpt PR 33656] - Migrate iframe-based Client Hint WPTs to import client...

Bug 1764967 [wpt PR 33656] - Migrate iframe-based Client Hint WPTs to import client hints lists, a=testonly

Automatic update from web-platform-tests
Migrate iframe-based Client Hint WPTs to import client hints lists

Introduce two new files into "client-hints/resources" to centralize the
dependencies of client hint token lists across javascript and python
tests:

  - export.js
  - clienthintslist.py

Eventually all Client Hints tests will be migrated to using these lists
to pare down the number of tests touched when creating new hints; this
CL pertains to the tests that depend on
"client-hints/resources/expect-client-hints-headers-iframe.py"

One of change is the query strings fed to
"expect-client-hints-headers-iframe.py" is now generated in
"client-hints/resources/feature-policy-navigation.js".

Another change is fixing tests related to `sec-ch-ua-platform` since we
added platform to client hints returned by default in
getHighEntropyValues in https://crrev.com/c/3389295.

Bug: 1304740
Change-Id: Id41ddbe1ee29c10f7b7c96a283f7eca2abec438b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3549556
Reviewed-by: Ali Beyad <abeyad@chromium.org>
Commit-Queue: Victor Tan <victortan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#993338}

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wpt-commits: 0f27025f24489190e35227dd768fc439599a759b
wpt-pr: 33656