build: Remove java classpath conventions

[devinrsmith]

This removes our custom configuration hierarchy, historically inherited from the "fishlib" days.

Follow-up to #5683

Note: unlike #5683, this migration does not aim to preserve the exact configuration dependencies that were inherited in the java-classpath-conventions hierarchy. The configuration conventions were overly broad, and didn't represent the real dependencies that each project has. As part of this, our dependency on org.jetbrains:annotations changed from an implementation dependency (inherited through the fishBase configuration) to a compileOnly dependency to better reflect how we actually depend on it. We might expect that the jetbrains annotations would be removed from our application runtime classpath entirely, but that is not the case - it turns out that one of our transitive dependencies has a runtime dependency on it:

org.jetbrains:annotations:13.0                                                                                                                                                                                       
\--- org.jetbrains.kotlin:kotlin-stdlib:1.9.10                                                                                                                                                                       
     +--- io.confluent:kafka-protobuf-provider:7.6.0                                                                                                                                                                 
     |    \--- io.confluent:kafka-protobuf-serializer:7.6.0                                                                                                                                                          
     |         \--- project :extensions-kafka                                                                                                                                                                        
     |              \--- project :server                                                                                                                                                                             
     |                   \--- project :server-jetty                                                                                                                                                                  
     |                        \--- runtimeClasspath

In this case, it has the visible effect of "downgrading" our runtime classpath from what was previously org.jetbrains:annotations:24.0.0 to org.jetbrains:annotations:13.0. Arguably, this is the more correct runtime dependency to provide given it matches what the exact version the transitive library requests.