When drawing a table, some of the CSS properties must be moved from the
table grid box to an anonamyous table wrapper box. One of these
properties is `position`. `z-index` however is not. This leads to the
following behavior if a table has both `position` and `z-index`:
* The wrapper box has the `position`, but a `z-index` of `auto`.
* The grid box has the `z-index`, but `position: static`.
This effectively means that the `z-index property is ignored since it
has no effect on non-positioned elements. This behavior contradicts what
other browsers do and causes layout issues on websites.
To align Ladybird behavior with other browser this commit also moves the
`z-index` property to the wrapper box.
