Custom k8s environment variables for Node-RED applications

### Description

Presently, Node-RED apps in k8s have a set of environment variables that cannot be added to. This makes setting custom environment variables impossible without using k8s webhooks.

For example, in our use case, we want to be able to set a `HOST_IP` environment variable that makes use of k8s `fieldRef` to get the IP address of the node that the pod is running on. This is because we have a node-level Open Telemetry collector running on port `4317` accessible via the node's IP address. By using this functionality, we would always get the right IP address regardless of the node that a Node-RED app is running on.

An example of additional environment variables for a container's `env` setting is given below:

```
- name: OTEL_SERVICE_NAME
value:
- name: HOST_IP
valueFrom:
fieldRef:
apiVersion: v1
fieldPath: status.hostIP
- name: OTEL_EXPORTER_ENDPOINT
value: http://$(HOST_IP):4317
```

### Requested By

- Customer name and/or link to HubSpot contact
- https://app-eu1.hubspot.com/contacts/26586079/company/7761278700