adding support for MinReadySeconds in statefulsetspec

[DanielePalaia]

This closes #

https://app.zenhub.com/workspaces/service-operator-experience-623895d9b17eb7001156689f/issues/rabbitmq/service-operator-experience/143

Note to reviewers: remember to look at the commits in this PR and consider if they can be squashed

Summary Of Changes

Adding the possibility to override the field minimumReadySeconds in the statefulsetspec

Additional Context

This feature seems not to be enabled by default in K8s < 1.25 but we need to setup --feature-gates=StatefulSetMinReadySeconds=true

This can be done with minikube in this way: minikube start --cpus 12 --memory 12000 --feature-gates=StatefulSetMinReadySeconds=true

Local Testing

Please ensure you run the unit, integration and system tests before approving the PR.

To run the unit and integration tests:

$ make unit-tests integration-tests

You will need to target a k8s cluster and have the operator deployed for running the system tests.

For example, for a Kubernetes context named dev-bunny:

$ kubectx dev-bunny
$ make destroy deploy-dev
# wait for operator to be deployed
$ make system-tests