Update mentions of 'scroll container' to refer to scrollable axises when appropriate. #12289

[tabatkins]

WIP

Specs which mention scroll container:

• css-2024: n/a
• css-2025: n/a
• css-2026: n/a
• css-align-3: mixed references; some care about the scroll axis, others don't
• css-anchor-position-1: always cares about the scroll axises
• css-backgrounds-3: only background-attachment:local, doesn't care about axises
• css-backgrounds-4: ditto
• css-conditional-5: scroller CQs only establish CQ containers for their scrollable axises
• css-display-3: doesn't care about axis
• css-display-4: ditto
• css-flexbox-1: minimum content size cares that the main axis is scrollable
• css-flexbox-2: ditto
• css-grid-1: n/a
• css-grid-2: n/a
• css-multicol-2: n/a
• css-nav-1: a few bits care about whether you can scroll in a direction; these are now axis-aware
• css-overflow-3: edits are already committed
• css-overflow-4: scrollbar mentions, implicitly already about axises
• css-overflow-5: TODO: hmm, unsure about scroll markers
• css-overscroll-1: Only chain to scrollers that are scrollable in that axis.
• css-position-3: stickypos cares about axises
• css-position-4: n/a
• css-scroll-anchoring-1: i don't think i need to do anything here? the algos look okay as they are, i think
• css-scroll-snap-1: TODO: leaving alone until the WG decides if snapping on different boxes should happen or not
• css-scroll-snap-2: same
• css-scrollbars-1: n/a
• css-sizing-4: auto min size, and min-intrinsic-size, care about axises, since they care about scrollability in that axis to reach something
• css-ui-3: not touching, RECish
• css-ui-4: resize doesn't care about axis
• css-writing-modes-4: just a note mention
• cssom-view-1: adjusted "potentially scrollable" to be axis aware, so scrollLeft/Top will care properly about scroll axis on body
• scroll-animations-1: all the timelines care about axis

[flackr]

Overall this looks good, just wanted to get clarification on a couple things.