Add Code Coverage for functional gradle tests / Gradle Test Kit

[wba2hi]

Is your feature request related to a problem? Please describe.
Code Coverage can not be generated out of the box for Gradle Test Kit tests. Gradle Test Kit tests are used inside VssProcessorPluginTest.

Describe the solution you'd like
The JacocoRootReport should also contain code coverage from the Gradle Test Kit tests.

Additional context

• https://github.com/koral--/jacoco-gradle-testkit-plugin
• https://discuss.gradle.org/t/gradle-plugins-integration-tests-code-coverage-with-jacoco-plugin/12403
• https://discuss.gradle.org/t/testkit-jacoco-coverage/18792/4
• the package '**/vssprocessor/plugin/**' was excluded from the jacocoRootReport, it's exclusion should be reverted once the test execution is correctly calculated