Print some progress messages

Appmap-java currently gives no indication that it's loaded and operating correctly. This can make troubleshooting difficult since the only way to check is to look for side-effects (like creating maps or generating the config file); this is made all the more important seeing how difficult it can be to thread the java agent settings through some environments.

Consider appmap-node:

$ appmap-node index.js
(Λ) Running with appmap-node version 2.23.2
(Λ) Using config file /home/divide/projects/example/appmap.yml
...

A short message like this would give a lot of reassurance that the agent is indeed loaded and initialized. It could also print paths to generated maps and/or a summary at the end ("generated n maps in /path").

Start by tracing appmap-java's agent initialization and map-generation flow, then compare the progress output shown for appmap-node. Done means the agent reports that it loaded and initialized, with useful generated-map or completion information where available; verify the behavior using the project's existing tests or agent execution checks.