Add convention plugin for classpath-based applications

[jjohannes]

As many projects as possible should use the Java Module System (Module Path) for compilation and runtime.
However, there are example/tool projects where this is very hard to achieve because they pull in another framework that is not ready for the Modules System (e.g. Spring, Google Cloud Platform).

It would be good to have a standard setup for those (sub)projects that allows them to use the classpath while still having all the checks, including dependency analysis, in place.

Currently affected projects:

• https://github.com/hashgraph/hedera-sdk-java/tree/main/tck
• feat: Tool for converting Record Files to Block Stream hashgraph/hedera-block-node#389