Make consistentHashing to a generic tools class

[maobaolong]

What changes are proposed in this pull request?

Make ConsistentHashing to a generic tool class, so that we can use it in various place.

[alluxio-bot]

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• PR title follows the conventions: FAIL
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[alluxio-bot]

Automated checks report:

• PR title follows the conventions: PASS
• Commits associated with Github account: PASS

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