feat: add supplementalGroups support to helm chart security context

[y-eight]

Summary

This PR adds support for the supplementalGroups field in the pod security context configuration for the f5-bigip-ctlr helm chart. This allows users to specify additional group IDs that should be applied to the container process.

Changes

• Added supplementalGroups example in values.yaml
• Updated deployment template to render supplementalGroups when specified
• Tested with helm template and kubectl dry-run validation

Testing

The changes have been tested using:

• helm template without supplementalGroups (validates default behavior remains unchanged)
• helm template with supplementalGroups set via --set flag
• helm template with supplementalGroups specified in a custom values file
• kubectl apply --dry-run=client to validate the generated YAML

Test Results

Without supplementalGroups (default behavior):

securityContext:
  runAsUser: 1000
  runAsGroup: 1000
  fsGroup: 1000

With supplementalGroups enabled:

securityContext:
  runAsUser: 1000
  runAsGroup: 1000
  fsGroup: 1000
  supplementalGroups:
    - 1000

All tests passed successfully with valid Kubernetes manifests.