prometheus-adapter: Collect metrics from Prometheus Adapter

Update default ciphers used by kube-rbac-proxy

secure metrics port for scheduler and controller-manager

Remove instance:node_filesystem_usage:sum

jsonnet: update component versions

Regenerate dashboards and prometheus alerts

Merged https://github.com/kubernetes-monitoring/kubernetes-mixin/pull/463 to remove duplicate entries for memory usage, however I'd like to move these changes to the Prometheus-Operator helm chart(https://github.com/helm/charts/pull/23024#issuecomment-661967101). I've regenerated the dashboards/alerts.

Add PrometheusOperatorListErrors and fix PrometheusOperatorWatchErrors threshold 

Watch error alert

chore(jsonnet):   update jsonnet to master

prometheus-operator.libsonnet: Add PrometheusOperatorWatchErrors alert

pulls in recent performance improvement changes to speed up rendering

resolves #537

jsonnet/kube-prometheus: Bump default versions of prometheus and alertmanager

enable etcd latency metrics in kube-apiserver

kube-apiserver has a histogram etcd_request_duration_seconds that
measures latency between the kube-apiserver and etcd instance.
This metrics is currently dropped by cluster-prometheus. Enable
this metrics so we have visibility into etcd latency.

We ensured that this does not enable other unwanted metrcis

count by(name) ({name=~"etcd_request.+"})

etcd_request_duration_seconds_bucket
etcd_request_duration_seconds_count
etcd_request_duration_seconds_sum

Update the Issue templates to redirect to GitHub Discussions.

Update kubernetes-mixin to remove KubeAPILatencyHigh & KubeAPIErrorsHigh

Fix typo

Bump Grafana to v6.7.4