Support go.kubebuilder.io/v4

[hj-johannes-lee]

Is your feature request related to a problem? Please describe.
operator-sdk requires go.kubebuilder.io/v4 from v.1.38.0 ref Current version is v2. It seems that the change is also related to the removal of rbac-proxy.

Describe the solution you'd like
Update the version to v4.

Describe alternatives you've considered
Use old version (v1.37.0 or less) of operator-sdk until updated.

Additional context

[mythi]

@hj-johannes-lee we should be at v4 level. We just don't follow their scaffolding and many of the v2->v3->v4 migrations have been implemented manually. Did you spot any gaps?