Add web platform test for CSP frame-ancestors with path

[chromium-wpt-export-bot]

The CSP frame-ancestors checking algorithm matches the frame
ancestor's origin against the source list. An origin will never match
a URL with a path in the source list. Hence this CL adds a web
platform test checking that frame loads are blocked if frame-ancestors
includes a URL with a path.

Bug: 40780874
Change-Id: I33a461a1f69b040d8a5e803978161352821d4161
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6094569
Reviewed-by: Antonio Sartori <antoniosartori@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1397345}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[dev-ansung]

WPT Command: python3 ./wpt run --channel=nightly --verify --verify-no-chaos-mode --verify-repeat-loop=0 --verify-repeat-restart=10 --github-checks-text-file=/home/test/artifacts/checkrun.md --affected base_head --log-mach-level=info --log-mach=- -y --no-pause --no-restart-on-unexpected --install-fonts --no-headless --verify-log-full --binary=/home/test/build/firefox/firefox firefox

Some affected tests had inconsistent (flaky) results:

Unstable results

Test	Subtest	Results	Messages
/content-security-policy/frame-ancestors/frame-ancestors-path-ignored.window.html	A 'frame-ancestors' CSP directive with a URL that includes a path should be ignored.	FAIL: 2/10, PASS: 8/10	assert_unreached: The IFrame should have been blocked (or cross-origin). It wasn't. Reached unreachable code

These may be pre-existing or new flakes. Please try to reproduce (see the above WPT command, though some flags may not be needed when running locally) and determine if your change introduced the flake. If you are unable to reproduce the problem, please tag @web-platform-tests/wpt-core-team in a comment for help.

[dev-ansung]

created https://crbug.com/385786172
@KyleJu @DanielRyanSmith can you help admin merge? Thanks!