Support `values.yaml.gotmpl` in charts valuesFiles

[ion-elgreco]

Is your feature request related to a problem? Please describe.

We can template things from values.files into charts[0].values with sourcePath and targetPath. However this makes everything quite verbose. I would rather want to provides a valuesFiles like this:

components:
  - name: helm-charts
    charts:
      - name: gateway-helm
        version: 1.7.0
        url: oci://docker.io/envoyproxy
        namespace: envoy
        valuesFiles:
          - ./gateway/values.yaml.gotmpl

Describe the behavior you'd like

valuesFiles in charts should support gotmpl versions of values.yaml so that we can simply have these values.yaml.gotmpl, and these values will come from values.files in the root

global:
  images:
    ratelimit:
      image: "{{ .Values.containerRegistry }}/{{ .Values.envoy.ratelimit.repository }}/{{ .Values.envoy.ratelimit.tag }}"

deployment:
  envoyGateway:
    image:
      repository: "{{ .Values.containerRegistry }}/{{ .Values.envoy.repository }}"
      tag:  "{{ .Values.envoy.tag }}"