[IR Framework] Make AbstractInfo.getRandom() static

To use the dedicated (private static final) Random object of AbstractInfo one needs to use the non-static getRandom() method like this:

@Run(test = "myTest")
public void runMethodForMyTest(RunInfo info) {
   int x = info.getRandom().nextInt();
   myTest(x);
}

It would be easier to make getRandom() static to provide an easier access to it without the need to specify RunInfo as parameter:

@Run(test = "myTest")
public void runMethodForMyTest() {
   int x = RunInfo.getRandom().nextInt(); // or AbstractInfo.getRandom().nextInt()
   myTest(x);
}