[dartdevc] Send log messages to injected client instead of chrome console

[annagrin]

Currently we send log messages to chrome console where they can get truncated, so dwds never receives a full message and cannot communicate it to the users. We should send a log event with the full message to the dwds's injected client instead, similar to what we already do for postEvent and registerExtension methods.

See discussions in flutter/devtools#3222 and flutter/flutter#47913

Related: dart-lang/webdev#1619