Yxjetcd rangestream

[yangxuanjia]

Please read https://github.com/etcd-io/etcd/blob/master/CONTRIBUTING.md#contribution-flow.

#12342
I will make an topic for resolve #12342 , and make test futhermore.
If maintainer think this PR is good, I will do the following things.(unit test, proxy rangestream and lease reagestream)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 21 days if no further activity occurs. Thank you for your contributions.

[gyuho]

We will revisit this very soon, targeting etcd 3.6. /cc @chaochn47

[yangxuanjia]

rangeStream we use it for k8s big range to resolve OOM problem.
I modify the inner rangeStream version include etcd, grpc-proxy.
combine rangeRequest prototype for range and rangeStream.
If need, I will update the code for this PR again.

this PR code version is old.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 21 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 21 days if no further activity occurs. Thank you for your contributions.

[linxiulei]

Is this still WIP?

I am working on #14810 that shares the idea on #12343 (comment) and it uses pagination so it won't break the queries.

[ptabor]

It's kept in the backlog - it doesn't seem there is a maintainer that has capacity to proceed with the project,
but technically it looks like a right thing to do.
Improving the reliability is definitely higher priority than this.

[k8s-ci-robot]

PR needs rebase.

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