[3.4] Backport clientv3: Replace balancer with upstream grpc solution

[chaochn47]

Part of #16740

This PR fully removes etcd customized implementation of gRPC old balancer API without breaking changes.

Backported

• clientv3: simplify grpc dialer usage. #11574
• clientv3: Replace balancer with upstream grpc solution #12671
• clientv3: PS: Replace balancer with upstream grpc solution #12706 (stripped grpc proxy changes)
• client: call .Endpoints() in dial() in client/v3/client.go instead of accessing cfg.Endpoints directly #13203
• Fix http2 authority header in single endpoint scenario #13359 (only e2e test is implemented, corresponding integration test is not deserved to be back-ported given its risk caused by large number of test code changes)
  • Refer to [3.4] Backport #12671 clientv3: Replace balancer with upstream grpc solution #16844 (comment)

#16826 should be merged first and this PR will be rebased on top of that.

This should allow us bump gRPC to v1.51.0 easier in release-3.4 in the follow up PR.

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

[ahrtr]

@chaochn47 please rebase this PR. thx

[chaochn47]

@ahrtr

This PR has been rebased. PTAL one commit at a time, thanks~

[ahrtr]

This is a huge PR. Could you break down this PR, such as backporting each PR in the list separately?

[chaochn47]

This is a huge PR. Could you break down this PR, such as backporting each PR in the list separately?

It's doable.

Just want to confirm that even if the backported PR introduces bug, it's okay to backport the fix separately, correct?

[ahrtr]

Just want to confirm that even if the backported PR introduces bug, it's okay to backport the fix separately, correct?

I think so. The goal right now is to break down this huge PR to make the reviewing easier.

[chaochn47]

Just want to confirm that even if the backported PR introduces bug, it's okay to backport the fix separately, correct?

I think so. The goal right now is to break down this huge PR to make the reviewing easier.

First one is out.

[ahrtr]

@chaochn47 are you still working on backporting the last PR?

[chaochn47]

Yeah, I will help my colleague @jasdel to finish the remaining gRPC version upgrade to resolve the CVE.

Is there a deadline so we can adjust the priorities on our TODO list?

[ahrtr]

It's a blocker for #16751. I expect it can be resolved asap to unblock the release of 3.4.28 (which includes fixes to two CVEs). Thanks.