test(smoketest): use -agent-equipped -reports sidecar

[andrewazores]

Based on top of #1028
Related to #520

This PR builds on top of #1028 with the pluggable discovery API and combines cryostatio/cryostat-reports#45 / cryostatio/cryostat-agent#4 for testing/demonstration purposes. The end result when everything is rebuilt, configured (as in smoketest.sh here), and run, is that the cryostat-reports sidecar container is deployed with a cryostat-agent attached. -reports no longer enables JMX and so is not connectable for typical Cryostat actions like listing event types or manually starting recordings, but it is still available for its report generation sidecar purpose. The attached -agent is configured to talk to the Cryostat server instance. It registers itself as a Discovery Plugin via the new #1028 API, then publishes a self-description discovery node with some metadata about itself and a dummy http connectUrl. It then starts a managed Flight Recording within the cryostat-reports application and periodically pushes JFR binary files to the Cryostat server archives.

• feat(discovery): pluggable discovery services API (feat(discovery): pluggable discovery services API #1026)
• feat(discovery): persistence and callback URL handling (feat(discovery): persistence and callback URL handling #1029)
• rebase fix
• feat(discovery): use hibernate, h2database, postgresql (feat(discovery): use hibernate, h2database, postgresql #1032)
• itest fixup
• apply spotless
• periodically prune unreachable discovery plugins, and require unique callback URLs
• fixup! periodically prune unreachable discovery plugins, and require unique callback URLs
• reorder latch countdowns
• document new variables
• test(smoketest): use agent-equipped build of report sidecar
• configure -reports without JMX