UCP: additionalPrinterColumns tidbautoscaler (#1943)

[sre-bot]

cherry-pick #1943 to release-1.1

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What problem does this PR solve?

UCP: #1820

What is changed and how does it work?

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

kubectl -n t1 apply -f examples/basic/tidb-cluster.yaml
kubectl -n t1 apply -f examples/basic/tidb-autoscaler.yaml
kubectl -n t1 get ta 
NAME       TIDB-MAXREPLICAS   TIDB-MINREPLICAS   TIKV-MAXREPLICAS   TIKV-MINREPLICAS
basic-autosacler   5                  2                  5                  2

Code changes

• Has Go code change

Side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Does this PR introduce a user-facing change?:

NONE