- Removes workarounds in test-run-native_calls for ARM and
  adds ARM 32-bit aliasing-aware register allocation.
- Uses wasm::LinkageAllocator instead of custom allocator to avoid
  duplication of this logic.
- Fixes a problem in wasm::LinkageAllocator with high 16 VFP regs,
  and makes member variable naming consistent.

Bug: v8:8015
Change-Id: Ie8bb8bad06bebce2cef3da0f6ad5c59d5f3b3b36
Reviewed-on: https://chromium-review.googlesource.com/1199907Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55696}