First sidecar module: OpenTelemetry (#8013)

* remove opentelemetry from main nginx image

* add opentelemetry sidecar image

* handle extra modules in helm chart

* fix running helm chart

* mount the modules volume in the init container

* merge the mounted folder

* fix the otel image

* fix licence year

* fix cloudbuild image

* use the same nginx version as in the main image

* only retrieve /etc/nginx/modules for now

charts/ingress-nginx/values.yaml

@@ -559,6 +559,15 @@ controller:
   #   image: busybox
   #   command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
 
+  extraModules: []
+  ## Modules, which are mounted into the core nginx image
+  # - name: opentelemetry
+  #   image: busybox
+  #
+  # The image must contain a `/usr/local/bin/init_module.sh` executable, which
+  # will be executed as initContainers, to move its config files within the
+  # mounted volume.
+
   admissionWebhooks:
     annotations: {}
     # ignore-check.kube-linter.io/no-read-only-rootfs: "This deployment needs write access to root filesystem".