Merge envtest usage

Couldn't we use the `envtest` package we have in our repo?
And call it liken this
https://github.com/aws/eks-anywhere/blob/119aab6f6bceed10028b391a5d722828f8c2348d/controllers/main_test.go#L12-L14

_Originally posted by @g-gaston in https://github.com/aws/eks-anywhere/pull/3602#discussion_r991582161_

See the comment chain for details.

Start with controllers/main_test.go at the linked lines and locate the existing envtest package usage in the repository. Compare the current test setup with that example; done means the relevant tests use the repository's envtest package consistently and pass.

Written by the indexing model from the issue text.