generate istio destinationRule subset from pod-template-hash

[myname4423]

... and add fields to allow user set canary/stable subset name

Ⅰ. Describe what this PR does

Behaviors if this PR merged:

1. when work with Istio for trafficRouting, if spec.strategy.canary.disableGenerateCanaryService is set true and Istio DestinationRule is provided, Rollout will append a canary subset for DestinationRule. The stable subset(if not provided in DestinationRule, stable subset will be create also) and canary subset are distinguished by label selectors, which are respectively pod-template-hash of v1 and v2.

2. User is allowed to set subset name of stable subset and canary subset, via spec.strategy.canary.trafficRoutings[x].additionalParams, such as

      trafficRoutings:
      - customNetworkRefs: 
        - apiVersion: networking.istio.io/v1beta1
          kind: DestinationRule
          name: dr-demo
        - apiVersion: networking.istio.io/v1beta1
          kind: VirtualService
          name: vs-demo
        service: service-demo
        additionalParams:
          istio.destinationRule.stableSubsetName: "base" # defaults to "stable"
          istio.destinationRule.canarySubsetName: "canary" # defaults to "canary"

Ⅱ. Does this pull request fix one issue?

no

Ⅲ. Special notes for reviews

will update doc later

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[kruise-bot]

@myname4423: PR needs rebase.

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