Cannot configure image URI for PIA canary pods

[LeBoucEtMistere]

Currently when creating a RestateCluster Custom Resource in an AWS EKS cluster where the operator is installed, it will spin up canary pods during the deployment process that are tasked with validating the creation of the Pod Identity Associations (PIA) if this feature was enabled for the cluster.
The code spinning up the pods hardcodes the following image URI: busybox:uclibc (cf.

restate-operator/src/controllers/restatecluster/reconcilers/compute.rs

Line 782 in 028b956

image: Some("busybox:uclibc".into()),

)
This image URI is not configurable through the chart value file. This is a problem for environments where the URI needs to point to a private container registry. In these environments, this results in the PIA canary pods getting into an ImagePullBackoff state.

Proposed solution: make the PIA canary image configurable through the standard chart configuration mechanism (value.yaml files).

[tillrohrmann]

Thanks for raising this issue @LeBoucEtMistere. Your proposed solution sounds reasonable. Would you like to work on this change? cc @lukebond for visibility.