uma: Add KASAN state transitions

uma: Add KASAN state transitions

- Add a UMA_ZONE_NOKASAN flag to indicate that items from a particular
  zone should not be sanitized.  This is applied implicitly for NOFREE
  and cache zones.
- Add KASAN call backs which get invoked:
  1) when a slab is imported into a keg
  2) when an item is allocated from a zone
  3) when an item is freed to a zone
  4) when a slab is freed back to the VM

  In state transitions 1 and 3, memory is poisoned so that accesses will
  trigger a panic.  In state transitions 2 and 4, memory is marked
  valid.
- Disable trashing if KASAN is enabled.  It just adds extra CPU overhead
  to catch problems that are detected by KASAN.

MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D29456