Only log incrementally deserialized maps with --trace-maps instead of
iterating the whole heap and print all existing maps on every partial
deserialization for new contexts. This should greatly improve
performance of --trace-maps on websites with many iframes.

- Add helpers to share code: LogNewObjectEvents, LogScriptEvents,
  LogNewMapEvents
- Link AllocationSites before any GC

Change-Id: I5322421a83e057518f871540691511c80bc7786a
Reviewed-on: https://chromium-review.googlesource.com/c/1342029Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57874}