Use hawkeye to generate and check license

[daviderli614]

Use hawkeye tool to standardize license generation and check process, and use github action to check license.
Here is the template for the license header: license-header.txt.

All .go files defined in licenserc.toml should be added with license header.

Add Makefile to operate hawkeye:

• make hawkeye: install hawkeye.
• check-license: check license header.
• format-license: format license header.
• remove-license: remove license header.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: daviderli614
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[k8s-ci-robot]

Hi @daviderli614. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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