[scroll-animations-1] Change tests to reflect the change in `timeline-scope`

[dshin-moz]

Test List

• scroll-animations/css/timeline-scope-all.html
• scroll-animations/css/timeline-scope.html
• scroll-animations/css/view-timeline-lookup.html

Rationale

As per resolutions (1, 2) and the corresponding change 3.

The change is designed to be low-impact on two aspects:

• Ancestor lookup happens first
• Timelines are now more visible by default, timeline-scope contains it

For all tests that refer to timeline-scope/timelineScope:

No change (Parsing & Computation):

• scroll-animations/css/timeline-names-ident-function.html
• scroll-animations/css/timeline-scope-computed.html
• scroll-animations/css/timeline-scope-parsing.html

No change (Used to ensure visibility, but flips to containing them, and there is no conflict):

• scroll-animations/css/animation-timeline-deferred.html
• scroll-animations/css/animation-timeline-ignored.tentative.html
• scroll-animations/css/animation-timeline-multiple.html
• scroll-animations/css/deferred-timeline-composited.html
• scroll-animations/css/scroll-timeline-dynamic.tentative.html
• scroll-animations/css/scroll-timeline-range-animation.html
• scroll-animations/css/timeline-offset-keyframes-hidden-subject.html
• scroll-animations/css/view-timeline-animation.html
• scroll-animations/css/view-timeline-dynamic.html
• scroll-animations/css/view-timeline-range-animation.html
• scroll-animations/css/view-timeline-subject-in-shadow-root-with-timeline-scope.html

Change required (Inner vs outer timeline containment, but "last in tree order" changes the matching, I think):

• scroll-animations/css/timeline-scope-all.html
• scroll-animations/css/timeline-scope.html

Change required (Conflict resolves by flat tree order, instead of being unresolved):

• scroll-animations/css/view-timeline-lookup.html

[emilio]

cc @fantasai @andruud

[graouts]

Cc @flackr and @kevers-google as well.

[hiikezoe]

scroll-animations/css/view-timeline-dynamic.html is currently filed under "No change (Used to ensure visibility, but flips to containing them, and there is no conflict)", but I think this test case actually belongs in "Change required (Conflict resolves by flat tree order, instead of being unresolved)" as well.

// Identical timelines in div75 and div25 creates an ambiguity.
div25.classList.add('timeline');
await waitForCSSScrollTimelineStyle();
assert_equals(getComputedStyle(target).zIndex, '-1', 'ambiguous');

[nairnandu]

reviewed with @kevers-google. LGTM.

[jgraham]

This may need further changes to align with w3c/csswg-drafts#13974