Template API and Metrics Base URLs

[ianstanton]

We currently need to pass the following environment variables to temboUI:

    env:
      - name: NEXT_PUBLIC_API_BASE_URL_V1
        value: "http://api.gcp.tembo-software.com/api/v1"
      - name: NEXT_PUBLIC_METRICS_BASE_URL
        value: "http://dataplane.gcp.tembo-software.com"

This PR templates these values, reducing the input values the user needs to define.