feat: added chart hardened Kubelet

[CerRegulus]

Expose kubelet metrics

Added hardened kubelet to deploy hardened kubelet pushproxy on port 10250.

Motivaiton

Rancher doesn't host kubelet as a pod, so no metrics are directly parsed from it. Since the central DTIT monitoring solution (Dynatrace) needs kubelet metrics to be able to monitor PVCs, we should find a way to expose the kubelet metrics, so that:

• prometheus can gather them
• dynatrace has direct access to them as well

Additionally, all prometheuses aren't currently able to parse the kubelet serviceMonitor, even though it's deployed.

Even more additionally, the dynatrace active gate cannot parse the port, as no pod is to be found behind that IP. The logs below are from s01:

org.apache.http.conn.ConnectTimeoutException: Connect to 10.125.40.115:10250 [/10.125.40.115] failed: connect timed out
        at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:151)

TODOS

2. Deploy to staging
3. Make sure the metrics are exposed on port 10250 of the pushproxy pod
4. Check that the kubelet serviceMonitor is healthy again in prometheus
5. Check with the Dynatrace colleagues, that the problem is now solved and the one

[puffitos]

Please change the version of the chart to 0.10.0-rc1 or something similar, so we can test it in staging. Then you should be able to create a chart release by tagging the main branch.

[puffitos]

LGTM. The kubelet serviceMonitor is getting scraped and everything works as expected. The failing prometheus scrape is because of a certificate problem on some nodes in our development environment.