Previously, has_scrollable_overflow was a purely geometric check, true
whenever content extended beyond the padding box regardless of the
overflow property. This caused unnecessary scroll frame allocation for
boxes with `overflow:visible`.
Per CSS Overflow 3, scrollable overflow is only defined for scroll
containers (overflow: auto/hidden/scroll). Gate the flag on
`is_scroll_container()` so that only actual scroll containers get scroll
frames assigned.
This change removes premature reset of
`block_container_y_position_update_callback`. Also makes callback
private in `BlockMarginState`, because resetting it independently of
currently accumulated margins is incorrect.
Lots of test expectations are updated, but there is no visual
difference.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/6074
Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
...with inline children. This fixes an issue when we ignore abspos boxes
contained by PaintableWithLines while calculating overflow rect size.
Lots of layout tests are affected, because now PaintableWithLines has
overflow rect.
`Text/input/DOM/Element-set-scroll-left.html` is also affected and now
matches other browsers.
We used to subtract the maximum right margin of any containing box,
but we want to subtract the entire right margin instead. This yielded
incorrect intrusions for right floats not placed in the root.
