add 2 fields to status to support showing result of kubectl get

[myname4423]

Ⅰ. Describe what this PR does

if we run kubectl get rollout rollouts-demo, we get result like this:

the CANARY_STEP and CANARY_STATE are read from rollout.status.CanaryStatus, however, if we support blue-green, we cannot read the values from this path anymore, because the CanaryStatus will be nil. Therefore, i add copies of these two fields to rollout.status. They are only used to showing the brief result returned from kubectl get command.

Ⅱ. Does this pull request fix one issue?

no

Ⅲ. Special notes for reviews

[zmberg]

/lgtm

[zmberg]

/approve

[kruise-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zmberg

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