With this change, we now have ~1200 CellAllocators across both LibJS and
LibWeb in a normal WebContent instance.
This gives us a minimum heap size of 4.7 MiB in the scenario where we
only have one cell allocated per type. Of course, in practice there will
be many more of each type, so the effective overhead is quite a bit
smaller than that in practice.
I left a few types unconverted to this mechanism because I got tired of
doing this. :^)
This makes use of the new [UseNewAKString] extended attribute. Using
Vector storage will make it easier to make this interface into an IDL
iterable. It seems the reason it didn't use Vector originally was due
to awkward DeprecatedString -> String conversions.
