[VL] Minor class name / package name clean-ups

[zhztheplayer]

1. exec.Runtime -> runtime.Runtime as exec collides with execution
2. Scala test suites with name ...Test changed to use Suite as suffix
3. Simplify class names ...FuzzerTest to ...Fuzzer

[github-actions]

Thanks for opening a pull request!

Could you open an issue for this pull request on Github Issues?

https://github.com/apache/incubator-gluten/issues

Then could you also rename commit message and pull request title in the following format?

[GLUTEN-${ISSUES_ID}][COMPONENT]feat/fix: ${detailed message}

See also:

• Other pull requests

[PHILO-HE]

Thanks!