LibWeb: Start implementation of CSS Table 3 spec

Here I try to address bug where content of table overflows
it's width (hacker news is an example of such site) by
reimplementing some parts of table formatting context.

Now TFC implements first steps of:
https://www.w3.org/TR/css-tables-3/#table-layout-algorithm
but column width and row height distribution steps are
still very incomplete.

Userland/Libraries/LibWeb/Layout/TableRowGroupBox.h

@@ -16,8 +16,6 @@ class TableRowGroupBox final : public BlockContainer {
 public:
     TableRowGroupBox(DOM::Document&, DOM::Element*, NonnullRefPtr<CSS::StyleProperties>);
     virtual ~TableRowGroupBox() override;
-
-    size_t column_count() const;
 };
 
 }