- Removes primitive shuffle opcodes.
- Adds Shuffle opcode for S32x4, S16x8, S8x16.
- Adds code to ARM instruction selector to pick best opcodes for some
  common shuffle patterns.

LOG=N
BUG=v8:6020

Review-Url: https://codereview.chromium.org/2847663005
Cr-Commit-Position: refs/heads/master@{#45104}