Provide a way to delete keys and sequence elements during config strategic merge

[DmitriyMV]

Given:

cluster:
  apiServer:
    auditPolicy:
      apiVersion: audit.k8s.io/v1
      kind: Policy
      rules:
  controlPlane:
    endpoint: https://localhost:6443

This:

cluster:
  apiServer:
    auditPolicy:
      rules:
        - $patch: delete
          level: Metadata

Should work and result in

cluster:
  apiServer:
    auditPolicy:
      apiVersion: audit.k8s.io/v1
      kind: Policy
      rules: []
  controlPlane:
    endpoint: https://localhost:6443