Set default values for matchConstraints

[naoki9911]

Configure matchConstraints default values for MAP and VAP.
This is a follow-up of #13

$ kubectl explain validatingadmissionpolicy.spec.matchConstraints
GROUP:      admissionregistration.k8s.io
KIND:       ValidatingAdmissionPolicy
VERSION:    v1

FIELD: matchConstraints <MatchResources>

...

FIELDS:
  ...
  matchPolicy   <string>
  enum: Equivalent, Exact
    ...
    
    Defaults to "Equivalent"
    ...

  namespaceSelector     <LabelSelector>
    ...
    
    Default to the empty LabelSelector, which matches everything.

  objectSelector        <LabelSelector>
    ...
    Default to the empty LabelSelector, which matches everything.

$ kubectl explain mutatingadmissionpolicy.spec.matchConstraints
GROUP:      admissionregistration.k8s.io
KIND:       MutatingAdmissionPolicy
VERSION:    v1beta1

FIELD: matchConstraints <MatchResources>


...
FIELDS:
   ...

  matchPolicy   <string>
    ...

    Defaults to "Equivalent"

  namespaceSelector     <LabelSelector>
    ...
    
    Default to the empty LabelSelector, which matches everything.

  objectSelector        <LabelSelector>
    ...
    Default to the empty LabelSelector, which matches everything.