kmem: Add KASAN state transitions

Memory allocated with kmem_* is unmapped upon free, so KASAN doesn't
provide a lot of benefit, but since allocations are always a multiple of
the page size we can create a redzone when the allocation request size
is not a multiple of the page size.

Sponsored by: The FreeBSD Foundation

(cherry picked from commit 2b914b85ddf4c25d112b2639bbbb7618641872b4)