It seems that the difference between pending and ASAP in the spec is
only to allow the implementation to perform implementation-defined
operations between the two states. We don't need to distinguish the two
states, so lets just combine them for now.
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 only tracks whether the relevant steps should be executed at some
future (but very soon) time. This time will eventually be whenever the
"update animations and send events" procedure is invoked.
