KEP-4578: Feature Gate in etcd

[siyuanfoundation]

• One-line PR description: KEP to introduce feature gate in etcd

• Issue link: https://github.com/kubernetes/enhancements/issues/4578

• Other comments:

[siyuanfoundation]

/sig etcd

cc @serathius @ahrtr @logicalhan @jmhbnz @fuweid @stackbaek @henrybear327 @wenjiaswe

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[ahrtr]

The initial motivation is only to replace the existing new feature guidance with feature gate, so as to not break anything when graduating a feature.

The cluster level feature is a complicated topic, it's OK to discuss it separately.

[serathius]

/cc @liggitt For feedback about feature gates.

[serathius]

Some small nits, but overall proposal looks good to me.

[wenjiaswe]

/lgtm thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jmhbnz, serathius, siyuanfoundation

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• ~~keps/sig-etcd/OWNERS~~ [jmhbnz,serathius]

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[ahrtr]

Overall looks good to me. Thanks @siyuanfoundation for driving the effort.

[fuweid]

LGTM. Thanks @siyuanfoundation !