Upgrade to go/v4

[ShivangGoswami]

envtest was enabled on s390x via:
kubernetes-sigs/kubebuilder#3741

But the current hyper foil operator is based on go/v3

[root@XXXXX hyperfoil-operator]# operator-sdk
[Deprecation Notice] This version is deprecated.The `go/v3` cannot scaffold projects using kustomize versions v4x+ and cannot fully support Kubernetes 1.25+.It is recommended to upgrade your project to the latest versions available (go/v4).Please, check the migration guide to learn how to upgrade your project
...

as evident, current state of operator might cause issues with k8s version 1.25+ and envtest version for s390x is available from k8s 1.29.x
So we need to upgrade this repo to support operator sdk latest version

A lot of things have changed in operator-sdk now and the envtest module allows version to be mentioned within the makefile itself.
The current state uses a old shell script which is removed from the original repo now
Ref:
https://github.com/Hyperfoil/hyperfoil-operator/blob/master/Makefile#L104
https://github.com/kubernetes-sigs/controller-runtime/blob/v0.7.2/hack/setup-envtest.sh