LibWeb: Consider cell computed height in total row min height of table

Previously, the minimum height of a table row was calculated based
on the automatic height of the cells inner layout. This change makes
computed height of a cell boxes also be considered if it has definite
value.

Tests/LibWeb/Layout/input/table/cell-px-height.html

@@ -0,0 +1,17 @@
+<style>
+body {
+    display: table;
+}
+
+.row {
+    display: table-row;
+}
+
+.cell {
+    display: table-cell;
+    border: 1px solid black;
+    width: 100px;
+    height: 100px;
+}
+</style>
+<div class="row"><div class="cell"></div></div>