Converts k8s apiextensions v1beta1 to v1

[stinkyfingers]

Description

915.

• Switch Kubernetes API versions from */v1beta1 to */v1. After k8s 1.16, CustomResourceDefinions are in apiextensions.k8s.io/v1, rather than v1beta1.
• Upgrades controller-gen, so crdVersion will be v1 in the future.
• Upgrades kubebuilder version so bundled kube-apiserver will be >= kubernetes 1.16
• Adds check in unit tests to assure that k8s version is >= 1.16
• rbac.authorization.k8s.io/v1 and admissionregistration.k8s.io/v1 are also out of beta.
• Webhook manifests have slightly different structure.
• Lots of changes to the generated manifests.

Fixes # 915

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Chore (documentation addition or typo, file relocation)

Testing

• New tests were added with this PR that prove my fix is effective or that my feature works (describe below this bullet)
• This change requires no testing (i.e. documentation update)

Documentation

• All added public packages, funcs, and types have been documented with doc comments
• I have commented my code, particularly in hard-to-understand areas

Final Checklist:

• I followed standard GitHub flow guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings