This introduces:
- a way in d8 to send messages to the inspector and receive responses.
- a new test suite where existing debugger tests should migrate to.

R=jgruber@chromium.org, kozyatinskiy@chromium.org, machenbach@chromium.org
BUG=v8:5530

Review-Url: https://chromiumcodereview.appspot.com/2425973002
Cr-Commit-Position: refs/heads/master@{#40487}