Instantiate ValuesFrom before evaluating hash

[gianlucam76]

Ensures valuesFrom resources are fully instantiated/templated before calculating the hash used for change detection.

When a Helm chart utilizes valuesFrom (referencing a ConfigMap or Secret) and those resources contain Sveltos templates, Sveltos was previously calculating the hash based on the raw resource content rather than the instantiated content.

Example Scenario: A ConfigMap is used in valuesFrom with template annotations:

apiVersion: v1
kind: ConfigMap
metadata:
  name: cluster-values
  annotations:
    projectsveltos.io/template: ok
data:
  values.yaml: |-
    role: "{{ index .Cluster.metadata.annotations.role }}"

If the Cluster annotation role changed, the ConfigMap content itself remained the same (the template string didn't change), causing Sveltos to erroneously conclude that the Helm values were unchanged. Consequently, the Helm release was not updated to reflect the new metadata.

This was visible in the ClusterSummary Status.HelmReleaseSummaries valuesHash not changing:

status:
    dependencies: no dependencies
    featureSummaries:
    - featureID: Helm
      hash: kXmMfsd2tNKNIFA6xxnL+aq7XvIgSa4p36IuMpIRGcs=
      lastAppliedTime: "2026-01-21T07:33:42Z"
      status: Provisioned
    helmReleaseSummaries:
    - releaseName: vso
      releaseNamespace: hashicorp
      status: Managing
      valuesHash: jyi3q9pXIPMP4u7VlrPlq2ByKttMEPsuVW8tZQbl0KI=

This PR modifies the evaluation logic to:

1. Identify all resources referenced in the valuesFrom section.
2. Instantiate the content of those resources (resolving any templates) if necessary.
3. Evaluate the hash based on the final, instantiated values.

This ensures that any change in the underlying data (like Cluster metadata or referenced Secrets) changing the helm values, correctly triggers a Helm reconciliation.

Fixes #1591