Support kubectl‑kruise top cloneset

[GautamBytes]

This PR introduces the top cloneset command to kubectl‑kruise, allowing users to view aggregated CPU and memory usage for a CloneSet.

• Adds pkg/top/aggregator.go with pod‑metrics summation logic.
• Implements pkg/cmd/top/cloneset.go and updates pkg/cmd/top/top.go to register the new subcommand.
• Extends util.Factory interface for MetricsClient support.

Fixes #8

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[GautamBytes]

@furykerry , I will raise a diff pr for other remaining 4 workloads soon . You can check this one and tell if improvements are needed. Thanks!