This space contains objects which are larger than the size limits of other spaces.
Each object gets its own malloc’d region of memory.
Large objects are never moved by the garbage collector.
Precise allocation used for large objects (>= LARGE_CUTOFF).
Starlight uses mimalloc that already knows what to do for large allocations. The GC shouldn’t
have to think about such things. That’s where PreciseAllocation comes in. We will allocate large
objects directly using mi_malloc, and put the PreciseAllocation header just before them. We can detect
when a *mut GcPointerBase is a PreciseAllocation because it will have the ATOM_SIZE / 2 bit set.