Some of our environments prefer sized deletes, others don't support it

[flar]

In (permalink once flutter/engine#32088 lands needed) we need to supply a Deleter for our shared_ptr because it was allocated with an unexpected size. If we do not, then we get build failures downstream in environments that check for consistency between the new and delete operators.

We can supply a Deleter that calls the specific sized delete with the right size, which would be faster on those platforms, but unfortunately at least one environment (iOS) uses an allocator that does not provide the sized delete.

When all of our environments support sized deletes then we can provide the proper size.

[chinmaygarde]

@zanderso also suggested that we could use our own allocator in the engine. It may be premature though since we have only run into this issue once in the past few years.