Update Flux components to Kubernetes 1.31

[stefanprodan]

Update the Kubernetes Go packages and adapt to the breaking changes in controller-runtime v0.19 in all Flux projects and run conformance for Kubernetes 1.31.0.

Projects:

• cli-utils
• pkg
• source-controller
• kustomize-controller
• notification-controller
• helm-controller
• image-reflector-controller
• image-automation-controller
• flux2
• terraform-provider-flux