Add utility method getService() to Info object

[Stypox]

• I carefully read the contribution guidelines and agree to them.

In the client, it often happens that the StreamingService for an Info object needs to be obtained. Before, this could not be done inline and required 6 lines of code:

final StreamingService service;
try {
    service = NewPipe.getService(infoObject.getServiceId());
} catch (ExtractionException e) {
    // unreachable code
}

I added a shortand getService() method to the Info object, so now that whole lot of code is just replaced by infoObject.getService().