We previously tried to implement the [table specification algorithm] for
distributing the inline size of cells with `rowspan` > 1. This algorithm
isn't great though, so this change starts switching Servo to using an
algorithm like the one used in LayoutNG from blink. This leads to
improvements in test results.
Limitations:
- Currently, non-fixed layout mode is handled, but a followup change will
very likely addressed fixed mode tables.
- Column merging is not handled at all.
Fixes#6578.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>