- Renames select, swizzle, and shuffle to be consistent with the S128 and
  existing S32x4 ops, and reflect that these aren't arithmetic.
  e.g. I16x8Swizzle -> S16x8Swizzle.
- Implements S16x8 and S8x16 Select operations and tests.
- Implements S128And, Or, Xor, Not operations and tests.
- Implements Swizzle for 32x4 formats.
- Refactors test macros that generate SIMD code.

TEST=cctest/test-run-wasm-simd/*

LOG=N
BUG=v8:4124

Review-Url: https://codereview.chromium.org/2683713003
Cr-Commit-Position: refs/heads/master@{#43168}