arm64: Add pmap integration for KMSAN
- In pmap_bootstrap_san(), allocate the root PTPs for the shadow maps. (For KASAN, this is done earlier since we need to do some special bootstrapping for the kernel stack.)
- Adjust ifdefs to include KMSAN.
- Expand the shadow maps when pmap_growkernel() is called.
MFC after: 2 weeks
Sponsored by: Klara, Inc.
Sponsored by: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D43405