Currently CpuProfiler is a subclass of CodeEventListener, it listens code events
from Logger, constructs and stores CodeEventsContainer. This patch is part of
the effort to split the logic of CodeEventListener as ProfilerListener out of
the profiling functionality logic in CpuProfiler. A ProfilerListener will listen
to code events, construct code event to CodeEventsContainer and pass it to code
event handler.

The reason we refactor CpuProfiler is that eventually we want to move
CpuProfiler as part of sampler library and code event listener should stay
inside V8.

Main changes:
1. Refactored CpuProfiler into two parts, the CpuProfiler with profling
functionality and the ProfilerListener listening to code events from Logger.
2. Created CodeEventObserver and made CpuProfiler inherit from it.
ProfilerListener will have a list of observers and call CodeEventHandler once a
code event is created.
3. Moved code entry list from CodeEntry to ProfilerListener.

Minor changes:
1. Moved static code entry as part of CodeEntry.
2. Added ProfilerListener to Logger.

BUG=v8:4789

Review-Url: https://codereview.chromium.org/2053523003
Cr-Commit-Position: refs/heads/master@{#37112}