Previously, `greatest_child_width()` was used, which finds the maximum
margin box width among direct children. This is incorrect for tables,
whose width is determined by column distribution rather than by simply
finding the widest child. We now return the table's computed content
width instead, which already holds the correct value after layout.
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.
- Include vertical border spacing in row group offset calculation so
that they are axis-aligned with child row/cell elements. This makes it
so there isn't horizontal and vertical overflow caused by child
row/cell elements.
- Include horizontal border spacing in tr width calculations. This makes
it so tr elements don't have overflow anymore when there are multiple
columns.
- Apply vertical caption offset to row group top offset.
- Don't double-count top padding when calculating vertical offset for
tr and row groups.
