sync v1.17.0..v1.18.0 changes from upstream

[cofyc]

previous:

• sync v1.16.0..v1.17.0 changes from upstream #44

PRs:

• context in client-go kubernetes/kubernetes#87299 (this is incompatibility with Kubernetes client-go prior to 1.18, we should generate a client for k8s prior to 1.18)
• fix a bug that orphan revision cannot be adopted and statefulset cannot be synced kubernetes/kubernetes#86801
• apps/StatefulSets: Garbage collector should be able to orphan ControllerRevisions too kubernetes/kubernetes#84984
• Fix statefulset conversion kubernetes/kubernetes#87706
• Fix stateful set test flakiness kubernetes/kubernetes#90898

[cofyc]

https://github.com/kubernetes-sigs/clientgofix