`collapse_auto_fit_tracks_if_needed()` had a check that does collapsing
only if auto-fit is used like
`grid-template-columns: repeat(auto-fit, 1px);`, and it didn't work for
valid cases when `repeat(auto-fit)` is placed in the middle of
definition like `grid-template-columns: 1px repeat(auto-fit, 1px) 1px;`.
Reimplements `grid`, `grid-template`, `grid-template-rows`, and
`grid-template-columns` in a way that uses a separate function for each
grammar rule defined in the specification. This change results in many
additional passing tests from the already imported WPT suite. Most of
the remaining test failures are related to incorrect serialization of
grid properties.
It was annoying to maintain two separate but almost identical functions
that gradually accumulated small differences over time. This change
replaces them with a single function that resolves either width or
height, depending on the specified dimension.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
