Use a dynamically configurable timer for stack trace sampling

[JonasKunz]

Stack trace samples need to be taken at a as cosntant itnerval as possible. Tehrefore using a shared Thread pool is not an option. Isntead a custom high precision timer should be used which starts it's own thread.

Starting this timer when it is already running should be very low overhead and take no effect, as this will be done every time stack trace sampling gets activated for a method.

In addition the timer-thread should shut itself down after sopme period of inactivity (when stack trace sampling was not active for any method in that period),