Test link rel=compression-dictionary header as early hints

[fred-wang]

Spec PR: whatwg/html#11620

This is currently only implemented in Firefox but not covered by any test:
https://searchfox.org/firefox-main/rev/5e465cbe324a291bb69aa85c5c4231e052cabe9a/netwerk/protocol/http/EarlyHintsService.cpp#106

[fred-wang]

This is failing in Chromium, which I believe is expected per https://source.chromium.org/chromium/chromium/src/+/main:content/browser/loader/navigation_early_hints_manager.cc;bpv=1;bpt=1;l=406?q=content%2Fbrowser%2Floader%2Fnavigation_early_hints_manager.cc&ss=chromium%2Fchromium%2Fsrc

It's failing too in Igalia's WebKit branch for compression-dictionary, which I guess is expected as we currently don't modify https://searchfox.org/wubkat/rev/d221d71a6a560cb45bb3e9b23e526b6bcfa9e4b3/Source/WebKit/NetworkProcess/EarlyHintsResourceLoader.cpp#67

However, Firefox is failing even though it has some logic here: https://searchfox.org/firefox-main/rev/c86fcb7f22721f58a39455cb965da7634ecf88e6/netwerk/protocol/http/EarlyHintsService.cpp#106 ; so I will need to debug what's happening here edit: firefox now passes the latest version.

[fred-wang]

cc @TingPing @jesup @annevk @pmeenan

[wpt-pr-bot]

There are no reviewers for this pull request. Please reach out on the chat room to get help with this. Thank you!

[fred-wang]

This PR depends on #61119

[pmeenan]

LGTM, Thanks!