Drop `npm` (and possibly `node`) as runtime dependency of `kubeflow/dashboard`

### Checks

- [x] I have searched the [existing issues](https://github.com/kubeflow/dashboard/issues).
- [x] My request is related to one of the components in the [`kubeflow/dashboard`](https://github.com/kubeflow/dashboard) repository.

### Motivation

Currently the centraldashboard is being served via `npm start` as part of the `Dockerfile`:
https://github.com/kubeflow/dashboard/blob/41dc738d867161bc7e9d371ea69704cf0bc5f8c7/components/centraldashboard/Dockerfile#L19-L31

Optimally this dependency could be eliminated in the final part of the image in order to have less attack surface, especially given how old some parts of the components are.

### Implementation

The Dockerfile for `kubeflow/notebooks` (v2) could be a good inspiration for the implementation:

https://github.com/kubeflow/notebooks/blob/notebooks-v2/workspaces/frontend/Dockerfile

### Are you willing & able to help?

- [ ] I am able to submit a PR!
- [x] I can help test the feature!