The patch introduces a dedicated dispatching class for JIT code events. It is
set as a helper on the isolate.
This allows classes across v8 to break their dependency on Logger and CpuProfiler.
These two became just regular clients of the dispatcher.

BUG=v8:4789

Review-Url: https://codereview.chromium.org/2061623002
Cr-Commit-Position: refs/heads/master@{#37005}