feat(ingress-controller): add imagePullSecrets support with global fallback

[ArnaudCHT]

What

Add deployment.imagePullSecrets support in ingress-controller with fallback to global.imagePullSecrets.

Why

The ingress-controller deployment had no way to configure imagePullSecrets, forcing users to manually patch deployments or fork the chart.

Changes

• Add deployment.imagePullSecrets configuration option
• Falls back to global.imagePullSecrets if not set locally
• Backward compatible and works standalone

#883

Testing

To test this PR, you can use the following commands:

# Test with global.imagePullSecrets
helm template . -s templates/deployment.yaml \
  --set 'global.imagePullSecrets[0].name=global-registry-secret'

# Test with deployment.imagePullSecrets (local override)
helm template . -s templates/deployment.yaml \
  --set 'deployment.imagePullSecrets[0].name=my-registry-secret'

# Test priority: deployment takes precedence over global
helm template . -s templates/deployment.yaml \
  --set 'global.imagePullSecrets[0].name=global-registry-secret' \
  --set 'deployment.imagePullSecrets[0].name=my-registry-secret'

# Test standalone (no imagePullSecrets)
helm template . -s templates/deployment.yaml

[AlinsRan]

@ArnaudCHT Please resolve the conflict.

[ArnaudCHT]

@ArnaudCHT Please resolve the conflict.

done

[martin-schulze-e2m]

@AlinsRan @shreemaan-abhishek could you please approve the workflow run? Hopefully we don't need another round.

[martin-schulze-e2m]

@AlinsRan can you please give this another look?

[juzhiyuan]

cc @Baoyuantop

[Hathoute]

@shreemaan-abhishek can we have a new release of ingress-controller (to include this) ? thanks