Upgrade Parfait to support log4j2

[tallpsmith]

Log4j1.2 is now end of life. There are some key spots where Parfait uses Log4j's MDC context which will need to be migrated during the journey to Log4j2.

There are a few areas that we need to consider, and this might warrant separating these into a separate module (due to library dependencies). We could also decide whether to continue to support log4j1.2 at all.

Areas affected:

• io.pcp.parfait.timing.ThreadContext.MdcBridge
• General use of log4j1.2 logging (parfait-agent, and QuiescentRegistryListener)

[natoscott]

Yeah, nah. :-) See commit #85