Add a KPI to the data choices telemetry payload indicating the duration of the most recent OpenNMS core startup, from JVM start to state indicated by "Startup complete" in manager.log, in whole seconds.

The story this KPI tells is simple: "The most recent startup took X seconds". Having this information from systems in the real world, over time, will help us understand when a new release has improved (or worsened) startup time for many users.