Kubernetes: multi-node cluster and node-labelled pods

[YuryHrytsuk]

Deployment: AWS Master

The Kubernetes cluster shall consist of at least 2 nodes and the pods shall be constrained to particular nodes (e.g. simcore node or ops node like it is done on docker swarm via docker node labels)

### Tasks
- [x] Document how to add a new worker node (https://git.speag.com/oSparc/osparc-infra/-/merge_requests/251)
- [x] Document how to update node labels (https://git.speag.com/oSparc/osparc-infra/-/merge_requests/251)
- [x] ~~Assign simcore pods by default to simcore node via common helper chart?~~ WONT DO
- [x] Add CI Step to configure node labels (https://git.speag.com/oSparc/osparc-ops-deployment-configuration/-/merge_requests/964)
- [x] AWS Master: add 2nd node and add node labes (https://git.speag.com/oSparc/osparc-ops-deployment-configuration/-/merge_requests/960)
- [x] inhouse master: label k8s node (https://git.speag.com/oSparc/osparc-ops-deployment-configuration/-/merge_requests/965)
- [ ] https://github.com/ITISFoundation/osparc-ops-environments/pull/828

[YuryHrytsuk]

How to

Update cluster node labels:

• ansible-playbook -i $INVENTORY -b upgrade-cluster.yml --tags node-label
• source: https://computingforgeeks.com/kubespray-kubernetes-cluster-to-newer-release/
• ⚠️ to be refined and done according to official documentation
• tags documented: https://kubespray.io/#/docs/ansible/ansible?id=example-commands
• follow this question to understand if it is a proper solution: Label individual nodes/groups kubernetes-sigs/kubespray#2843 (comment)

Add new worker node (including configuration of new machine):

• ansible-playbook -i $INVENTORY scale.yml -b -v
• source: https://kubespray.io/#/docs/getting_started/getting-started?id=adding-nodes

Useful links

• kubespray add worker node to the cluster
• kubespray inventory doc