Add trace correlation to agent logs

[eyalkoren]

Is your feature request related to a problem?

When agent logs in ECS format, we can utilize log correlation to our logs as well.

Describe the solution you'd like

We can enhance our co.elastic.apm.agent.logging.Log4j2LoggerBridge to add to slf4j MDC before any logging event and removing after if the log format is JSON.

Describe alternatives you've considered

Another option is to utilize log4j extension capabilities - org.apache.logging.log4j.core.util.ContextDataProvider or org.apache.logging.log4j.core.ContextDataInjector

Additional context

Followup on #2428