talc looks complex (feature complete, but big enough to make me reluctant)
bumpalo looks less complex (still some wrinkles, but maybe workable)

It seems probably that I should be able to make one of those work. (not being able to deallocate with bumpalo makes it similar to heapless)

It seems like if I run out of local heap, I'd like to deallocate previously allocated items in order from oldest to newest.

This still makes me want to use `embedded-alloc` with a stable version of Box that impments `new_in`