USHIFT-2186: Multus CNI for MicroShift (#1545)

* multus CNI for microshift

* review changes

* race condition risk between multus readiness and workload start

* add intro to race condition between MicroShift and other networking init procedures

* explicitly mention /opt/cni/bin

* NetPol and webhook are non-goals

* add goal about providing IPAMs and CNIs

* improve workflows

- added explicit RHEL (rpm) sections
- explicitly mention NAD before the App using NAD

* `vlan` -> `ipvlan`; images will be part of OCP payload

* reword origin of thick plugin

* add "longer startup of Pods" drawback

* fix trailing whitespace

* extra networks will not support K8s' Service API

* supportability: kubelet & crio logs

* add open question about --namespace-isolation

* Remove mention of `default-network` annotation

It's not intended to be used in normal mode of operation.

* mention dhcp server

* test day 2 installation

* alternative: Cluster Network Operator based operator

* fix multus.kubeconfig path

* OpenShift uses thick plugin since 4.14

* fix NAD example with nil gateway

* Q: logging to file?

* update template

* risk: NAD reusing MicroShift's CIDR