Add code coverage reporting to Maven build

WF is using JaCoCo (https://docs.wildfly.org/26/Testsuite.html#creating-coverage-reports) so that could be mod_cluster's choice as well.

The setting up needs to be done in a way to account for multiple modules and also work for integration test suite (and Arquillian) that we will be adding.

Ideally this would be simply enabled by a single profile activation on a verify goal - to keep this in sync with WF - that should be mvn verify -P coverage.

Some random useful links

• Latest jacoco version - https://mvnrepository.com/artifact/org.jacoco/jacoco-maven-plugin
• Usage of aggregate-report goal - https://www.eclemma.org/jacoco/trunk/doc/report-aggregate-mojo.html
• Random example project to aggregate reports - https://github.com/jacoco/jacoco/wiki/MavenMultiModule
• Random GH plugin to give code coverage feedback on PRs - https://github.com/Madrapps/jacoco-report