IstioMeshGateway reconciliation does not honor spec.Deployment.Image value

[Tanemahuta]

Describe the bug
When reconciling an IstioMeshGateway with spec.deployment.image set, the image is not used in the deployment.

Steps to reproduce the issue:
Create

apiVersion: servicemesh.cisco.com/v1alpha1
kind: IstioMeshGateway
spec:
  deployment:
    image: my-repository.se/image-override:tag

Expected behavior
The deployment derived from the CR uses the image provided in the spec.

Additional context
Operator version: v2.11.6

[Laci21]

#820 merged