Move Reflections part to own gradle sub module

[de-jcup]

Situation

Currently sechub-doc contains Reflections implementation.
It is difficult to use the implementation in other sub modules, because normally no sub module has a reference to sechub-doc (except sechub-test, because this is for cross checking used)

Wanted

every gradle sub module shall be able to use Reflections class (but of course with project reference scope - means limitation in visible parts)

Solution

• Introduce sechub-reflections gradle sub module.
• Update sechub-doc (and other parts where necessary) to use this as a (test) dependency