Publish Wavefront metadata early so it is available in the dashboard

[shakuzen]

Currently, when clicking on the link output to logs on startup, it takes you to the Spring Boot dashboard (good!), but there is no information about the application you just started available there until after the first metrics publish, which is after 1 minute by default. I think this experience can be approved by publishing at least the Wavefront-specific metadata used to populate the Source / Application / Service dropdown menus at the top of the dashboard. If those were populated, then users would be able to tell that Wavefront knows about the application they just started.

Micrometer doesn't provide an API to publish metrics early, but since this is specific to Wavefront and Micrometer is delegating to the Wavefront SDK to publish metrics, one idea is to use the Wavefront SDK to publish a purely informational metric with the expected metadata to populate the dropdown menus.