* Push docker images to ghcr.io instead of gcr.io
The `cloud_integration.yml` and `release.yml` workflows were modified to
log into ghcr.io, and remove the `Configure gcloud` step which is no
longer necessary.
Note that besides the changes to cloud_integration.yml and release.yml, there was a change to the upgrade-stable integration test so that we do linkerd upgrade --addon-overwrite to reset the addons settings because in stable-2.8.1 the Grafana image was pegged to gcr.io/linkerd-io/grafana in linkerd-config-addons. This will need to be mentioned in the 2.9 upgrade notes.
Also the egress integration test has a debug container that now is pegged to the edge-20.9.2 tag.
Besides that, the other changes are just a global search and replace (s/gcr.io\/linkerd-io/ghcr.io\/linkerd/).
* CNI add support for priorityClassName
As requested in #2981 one should be able to optionally define a priorityClassName for the linkerd2 pods.
With this commit support for priorityClassName is added to the CNI plugin helm chart as well as to the
cli command for installing the CNI plugin.
Also added an `installNamespace` Helm option for the CNI installation.
Implements part of #2981.
Signed-off-by: alex.berger@nexiot.ch <alex.berger@nexiot.ch>