[Task] Update discovery plugin registration scheme to match 2.4

[andrewazores]

Describe the feature

https://github.com/cryostatio/cryostat/pull/1650
https://github.com/cryostatio/cryostat/pull/1700
cryostatio/cryostat-agent#193

There were recent-ish changes in the 2.4 codebase to improve the reliability of discovery plugin registrations. I think the current registration system implemented in 3.0 is older than this and still based on the previous 2.3 implementation, which is generally the same but is missing some error handling and other internal details.

Anything other information?

No response

[andrewazores]

Along with this, the smoketest vertx-fib-demo instance(s) should be updated to 0.13.1.