[iommu][arm_smmu] Port shared stage-1 modules

Port the shared stage-1 VMSAv8-64 modules in
//zircon/kernel/dev/iommu/arm_smmu/common/ to Rust so they can be shared
across both SMMUv2 and SMMUv3 and compiled in both the unified Zircon
kernel crate (cfg(is_kernel)) and host unit tests (cfg(not(is_kernel))):

- common/env.rs: zero-cost SmmuEnv seam abstracting PMM page
  allocation/reclamation, physmap conversions, CPU data-cache cleaning,
  and PinnedVmObject physical range lookups. It also has the single
  observation point for stores into memory the SMMU hardware reads,
  SmmuEnv::observe_hw_visible_write, which reports a store to the host
  test hardware model and is a no-op in the kernel.
- common/constants.rs: shared IOMMU permission flags, page geometry
  constants, and operating mode enumerations.
- common/smmu_mode.rs: kernel.arm-smmu-mode parser and validator. It
  reads each <base_addr> token as the C++ parser's strtoul(.., 0) did,
  including that function's quirks, so that an existing command line
  selects the same mode.
- common/vmsav8_64.rs: VMSAv8-64 stage-1 page table descriptor helpers,
  permission lookup table, and the two functions through which every
  translation table store goes, write_pte and zero_table_page.
- common/page_cache.rs: intrusive LIFO translation table page cache.
  Trimmed pages are returned to the PMM in one batch, as in C++.
- common/translation_table.rs: 4-level translation table walk,
  allocation, cache-cleaning, and empty-table reclamation cursor.
- common/device_aspace.rs: stage-1 device address space managing the
  translation table hierarchy and RegionAllocator IOVA space.

Places where the Rust deliberately differs from the C++ are marked
with a "Temporary porting note:" comment.

Bug: 565848139
Test: fx build --host //zircon/kernel/dev/iommu/arm_smmu/tests:arm_smmu_tests
Test: arm_smmu_tests_binary
Change-Id: I9da77963238c6f8498c8204758c8dca8516badec
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1912407
Reviewed-by: Abdulla Kamar <abdulla@google.com>
Fuchsia-Auto-Submit: Dustin Green <dustingreen@google.com>
Reviewed-by: Adrian Danis <adanis@google.com>
Commit-Queue: Dustin Green <dustingreen@google.com>