- Remove macros.py
- Inlines macros into d8.js
- Remove dead code (macros and message templates)
  from js2c.py
- Remove empty src/js directory

Bug: v8:7624
Change-Id: I8dfb69f2f8cb3746b67de816ffc8eb305cbcdee6
Reviewed-on: https://chromium-review.googlesource.com/c/1400150
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58631}