Add API extension for Metrics-Server v0.4.0

[manusa]

Generate Java API client and model types for Kubernetes Metrics Server (Cluster-wide aggregator of resource usage data).

See also:

• https://github.com/kubernetes-sigs/metrics-server#installation
• https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

[manusa]

Support was added in:

• 21

• https://github.com/manusa/yakc/commit/396524db7bebb0754114f19065025e07f7d42bdf
• https://github.com/manusa/yakc/commit/0c6ea54bccfd90f68fbe2f9963fe613a36d96614
• https://github.com/manusa/yakc/commit/71481bb2f79c32541df4994044cf0a759ed4fb90
• https://github.com/manusa/yakc/commit/c094e23ca37dc5e0241e3b9bb993010f2af624f3