k8s.io/client-go/tools: support context for event recording

Using StartRecordingToSinkWithContext instead of StartRecordingToSink and
StartLogging instead of StartStructuredLogging has several advantages:

- Spawned goroutines no longer get stuck for extended periods of
  time during shutdown when passing in a context that gets canceled.
- Log output can be directed towards a specific logger instead of the global
  default, for example one which writes to a testing.T instance.
- The new methods return an error when something went wrong instead of
  merely recording the error.

That last point is the reason for deprecating the old methods instead of merely
adding new alternatives.

Setting a context when constructing an EventBroadcaster makes calling Shutdown
optional. It can also be used to specify the logger.

Both EventRecorder interfaces in tools/events and tools/record now have a
WithLogger helper. Using that method is optional, but recommended to support
contextual logging properly. Without it, errors that occur while emitting an
event are not associated with the caller.

hack/logcheck.conf

@@ -29,6 +29,8 @@ structured k8s.io/apiserver/pkg/server/options/encryptionconfig/.*
 # TODO next: contextual k8s.io/kubernetes/pkg/scheduler/.*
 # A few files involved in startup migrated already to contextual
 # We can't enable contextual logcheck until all are migrated
+contextual k8s.io/client-go/tools/events/.*
+contextual k8s.io/client-go/tools/record/.*
 contextual k8s.io/dynamic-resource-allocation/.*
 contextual k8s.io/kubernetes/cmd/kube-scheduler/.*
 contextual k8s.io/kubernetes/pkg/controller/.*