feature: add victoria-k8s-stack chart

[hagen1778]

I'd like to have a k8s chart that would help me to collect logs & metrics from services&applications that run in k8s clusters. Similarly to https://github.com/VictoriaMetrics/helm-charts/tree/master/charts/victoria-metrics-k8s-stack and #1909 I want it to be all-in-one solution for logs and metrics, including the following components:

• victoria-logs server for storing and serving logs. Should be adjustable with number of replicas, where each replica stores the complete copy of the data
• logs-collectors for receiving or pulling logs from discovered services&applications. Should respect victoria-logs replicas
• victoria-metrics cluster for storing and serving metrics
• vmagents for metrics collection and delivering
• Grafana with pre-defined datasource to query&visualize logs & metrics from victoria-logs and victoria-metrics servers, and list of provisioned dashboards
• vmauth for balancing read requests among multiple replicas of victoria-logs and victoria-metrics servers
• vmalert for running pre-defined and arbitrary alerting rules against victoria-logs servers
• vmalert for running pre-defined and arbitrary alerting rules against victoria-metrics servers
• alertmanager for accepting alerting notifications from vmalert