publish doesn't support general container images

Scenario: I have sidecar and init car containers that are built from source (Dockerfile) in my current repository. I like the simplified `publish` command for publishing images to ACR.

I tried to add a `predeploy` hook to publish these images to ACR:

```yaml
hooks:
predeploy:
run: |
docker build ../init-app -t init-app:latest
azd publish --from-package init-app:latest
```

This ended up creating a side effect of overriding `SERVICE_WEB_IMAGE_NAME` and I couldn't get it working as expected. I was blocked.

Should `azd publish` support more scenarios broadly than just publishing the "one image" defined as a service?