This adds support for unaligned load/store access to the DataView
backing store and uses byteswap operations to fix up the endianess
when necessary. This changes the Word32ReverseBytes operator to be
a required operator and adds the missing support on the Intel and
ARM platforms (on 64-bit platforms the Word64ReverseBytes operator
is also mandatory now).

This further improves the performance on the dataviewperf.js test
mentioned in the tracking bug by up to 40%, and at the same time
reduces the code complexity in the EffectControlLinearizer.

Bug: chromium:225811
Change-Id: I296170b828c2ccc1c317ed37840b564aa14cdec2
Reviewed-on: https://chromium-review.googlesource.com/1172777
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55099}