Allow for multiple ports for deployments and services

Only one port can be specified now for deployments and services.
This covers most of the cases and gives simplicity but some applications may want to expose multiple ports.

I'd like to treat it as an edge case rather than the default, as for really special cases custom k8s templates can be used.

Something like:

```yaml
harness:
deployment:
...
port: 80
additionalPorts:
- 8080
- 9000
```

Locate the deployment and service configuration entry points and the custom Kubernetes template handling mentioned in the issue. Trace how the single port is read and rendered, then verify that an additionalPorts list can produce the requested extra ports for both deployments and services without changing the existing single-port behavior.

Written by the indexing model from the issue text.