Include default template rules for Knative services

[praveenrewar]

Describe the problem/challenge you have
Versioned resources (with a generated name) are not taken into account for Knative services

Describe the solution you'd like
It would be great if kapp's default deploy config would be aware of knatives's references to Secrets and ConfigMaps
Slack thread

We can add template rules like one below for knative services to make kapp aware of CMs and Secrets.

# Manage versioned configmap into serving.knative.dev/v1
templateRules:
- resourceMatchers:
  - apiVersionKindMatcher: {apiVersion: v1, kind: ConfigMap}
  affectedResources:
    objectReferences:    
    - path: [spec, template, spec, volumes, {allIndexes: true}, configMap]    
      resourceMatchers:
      - apiVersionKindMatcher: {apiVersion: serving.knative.dev/v1, kind: Service}

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[mamachanko]

As it might go overlooked, there are now tests for default template rules too.