serialize outgoing messages via cbor to json if needed.

Change-Id: I6d0300ddc27e365b16671d19922f467e09adcc54
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1636681Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61973}