adds events to go sdk, changelog

[andrewpmartinez]

Example of using the new events.

ztx, err := ziti.NewContext(cfg)

serviceAddedChan := make(chan *rest_model.ServiceDetail, 1)

serviceAddedRemover := ztx.Events().AddServiceAddedListener(func(detail *rest_model.ServiceDetail) {
	serviceAddedChan <- detail
})

Tests are in the edge repo...as there is a circular dependency trying to run controllers for integration tests here. See draft PR here: openziti/edge#1501

[plorenz]

I don't love the kataras events library any more. I prefer something more type safe and with clearer concurrency. You do have type safe high level apis, so it doesn't matter from the consumer side.