[arch][mmu] Define and implement non-contiguous Map function

ZX-1424 #comment initial functionality in, need some callers

Change-Id: I98cf351bfc7cbc5665e94688fabc53c7fde3f452

[arch][mmu] Rename Map to MapContiguous

This is prep work for adding support for adding a non-contiguous map.

ZX-1424

Change-Id: I63a557a884cfe496cfee2fa58e9f9ec17ba18b8e

[arm64][mmu] Add support for guest aspace.

Due to the way VTCR_EL2 is dependent upon ID_AA64MMFR0_EL1.PARange, and
the fact that PARange is limited to 40-bits on Cortex-A53, we can't use
the same configuration as the user-space mappings for guest mappings.

This change adds the basic setup for handling guest mappings, but
doesn't contain the TLBI operations needed. Those will come in a follow
up.

Change-Id: I9538ccc81a2c3d4afd141d2e28d3196a967fc370

[vm][zx_status_t] Use zx_status_t throughout the vm layer

Change-Id: If40e2571cdbd382b7b90da90cdef40daf07a2bd0

[zircon][mxtl->fbl] Rename mxtl to fbl

Change-Id: Ie21b6498e1bfb0a7fa0315e40b9e5c3ee78646be

[kernel][vm] move kernel/kernel/vm to just kernel/vm

Change-Id: I8f724a9f8a61415712661d1fdd3dc4e1c70cf620