Migrate cf-k8s-controllers to a multi-group kubebuilder project

[acosta11]

Background

With the initial CRDs implemented in the single workloads.cloudfoundry.org group, we realized it may be better to organize the resources in separate groups. Because there is a relatively small blast radius to the change earlier on in the project, we should address the tech debt of a monolithic api group now.

See https://kubebuilder.io/migration/multi-group.html.

Follow the kubebuilder migration docs https://kubebuilder.io/migration/multi-group.html to reorganize the project to support multiple api groups.

Acceptance Criteria

Based directly on the multi-group kubebuilder documentation:
GIVEN/WHEN I view the github.com/cloudfoundry/cf-k8s-controller repository
THEN I see:

• The CFRoute and CFDomain custom resources are in the networking.cloudfoundry.org group

• The api directory is now an apis directory with workloads and networking subdirectories to hold the now separately organized resources

• The controllers directory now contains workloads and networking subdirectories to hold the now separately organized controllers

• The kubebuilder PROJECT file is marked as multigroup: true

AND WHEN I run tests
THEN I see the envtest based controllers/group.suite_test.go files correctly install CRDs to the test environment

Impact

Organizing custom resources and controllers more granularly in the controller repository allows for clearer separation of concerns between the different technical domains of the cf implementation.

Dev Notes

We expect the new directory structure to affect imports currently in use by the first set of cf api shim stories like:

workloadsv1alpha1 "code.cloudfoundry.org/cf-k8s-controllers/api/v1alpha1"

becomes:

workloadsv1alpha1 "code.cloudfoundry.org/cf-k8s-controllers/apis/workloads/v1alpha1"