Missing ability to set taints, tags and labels of nodepool

[samos123]

GKE container NodePool update API supports updating the taints however looks like this python library does not support this yet.

See here for more info: https://cloud.google.com/kubernetes-engine/docs/reference/rest/v1beta1/projects.locations.clusters.nodePools/update

The set_labels function that exists is for applying them at a cluster level, however we need them at the nodepool level.

[rashisht1]

Additionally, the ability to update labels, tags and gvnic is also missing in the python library.

[bourgeoisor]

Looks like the proto hasn't been updated yet. Investigating.

[bourgeoisor]

I can confirm there is some discrepancy internally, thank you for bringing this up! I will update this issue once it is fixed.

[bourgeoisor]

The upstream proto has been updated with taints, tags, labels, gvnic: https://github.com/googleapis/googleapis/blob/master/google/container/v1beta1/cluster_service.proto#L2196-L2209

Waiting for this PR to go through: #147