Support new zones label

[prashanth26]

What would you like to be added:
Support for new topology.kubernetes.io/zone label.

Why is this needed:
The failure-domain.beta.kubernetes.io/zone labels are deprecated now in k8s. The k8s now supports topology.kubernetes.io/zone labels. We need to support the latest labels to be compliant with k8s.

As suggested by @hardikdr - this logic has to be updated to support the new label in addition to the already existing label here and also in the extension providers

Path to be taken

• Update autoscaler to take values from both labels - autoscaler #70
• Enhance Gardener to apply the new label to all extension providers