[aws-eks] Support adding service accounts to imported clusters

it seems like ICluster interface doesn’t have addServiceAccount function. So it’s not possible to add service account to the existing cluster

Reproduction Steps

    const cluster = Cluster.fromClusterAttributes(this, clusterName, {
      clusterName: clusterName,
      kubectlRoleArn: 'arn:aws:iam::1111111:role/iam-role-that-has-masters-access'
    });

    const serviceAccount = cluster.addServiceAccount(id);

    serviceAccount.addToPolicy(new PolicyStatement({
      resources: ["arn:aws:s3:::testBucket"],
      actions: [
          "HeadBucket",
          "ListAllMyBuckets",
          "ListBuckets"
      ]
    }))

What did you expect to happen?

no error

What actually happened?

cluster.addServiceAccount is not a function

Environment

• CLI Version :1.64.1
• Framework Version:1.63.0
• Node.js Version:10.7.0
• OS :macos
• Language (Version):3.9.6

Other

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This is 🐛 Bug Report

[iliapolo]

Adding Service Accounts to imported clusters is indeed currently unsupported. Marking this as a feature request.

[github-actions[bot]]

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