This fixes a bug in the CSS Grid when there is a column and/or row gap,
as previously it would take the index of the incorrect column when
finding the `AvailableSize`.
There is a mild complication in the GridFormattingContext as the
OccupationGrid does not take into account the gap columns and rows that
later appear in the `Vector<TemporaryTrack>` columns and rows. The
PositionedBoxes are kind of a connection between the two, and so it's
now more explicit whether you would like to refer to a column by its
position taking into the gap columns/rows or not.
Fixes a bug where when you had spans that that were bigger than the
grid, would create enough tracks to accomodate them. When a fixed
position is given, there should be at a minimum a row/column available
for the track. The span will be truncated if there is no space for it
later.
A bug was found where grid items were being drawn outside of the grid if
the item had a large span and the grid was defined as having gaps
between the rows/columns.
This was caused by an erroneous calculation of the
{row,column}_{start,span} properties.
Add ability to use values passed to grid-template-columns and
grid-template-rows for CSS Grid layout within a repeat() function.
E.g. grid-template-columns: repeat(2, 50px); means to have two columns
of 50px width each.
When the indicated column-span is greater than the implicit grid (like
in cases when the grid has the default size of 1x1, and the column is
supposed to span any number greater than that), then previously were
crashing.
Ensure that when a grid item is passed with a span and a fixed end
position, that if the resulting start of this item is less than 0 then
it won't throw. This is a temporary measure until the correct
functionality is implemented.
Implement span correctly when indicated in the grid-column-start,
grid-row-start, etc. CSS properties. Previously it had been implemented
as if span was something that went alongside the position property, but
actually it seems like if you do 'span 3' in the grid-column-start
property, for example, this means it literally spans 3 blocks, and the
3 has nothing to do with position.
