This CL implements several things needed for full SIMD BE support in WASM:
* Global variables are now kept in little-endian order as per specification
* Added support for SIMD on BE in wasm interpreter
* Fixed several tests that didn't work on BE because input or output
  data were not using LE in-memory layout

Change-Id: I4542d13d09fd276e15b0fc39f02e4a58831f65e4
Reviewed-on: https://chromium-review.googlesource.com/1160484
Commit-Queue: Ivica Bogosavljevic <ibogosavljevic@wavecomp.com>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Aseem Garg <aseemgarg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55075}