Add log forwarding support for the logging gem #3301
Description
logging is a popular Ruby logging library that's similar to Java's log4j. Currently, the Ruby agent does not support automatic forwarding for this library. It translates mdc (mapped diagnostic context) key value pairs into attributes on log events. See the agent-spec (internal) for details.
The work in #2399 may be relevant here, since both libraries have user-defined attributes on log events.