Remove MINIMUM_OBJECT_SIZE

Remove MINIMUM_OBJECT_SIZE

MINIMUM_OBJECT_SIZE would make all cached objects at least 0x80 bytes, which
would limit the number of objects in each slab to 31 objects.

This limitation is not needed, as the slab's mask is dynamically allocated to
cope with the correct number of objects that can fit into a single slab.
Cache object's sizes are rounded up to the nearest pointer boundary to maintain
object alignment. Removing the minimum size allows more objects per cache slab,
reducing the memory overhead of caches.

Signed-off-by: Owen Smith <owen.smith@citrix.com>