client Sync should exclude learner endpoint

[yishuT]

What happened?

We see etcdserver: rpc not supported for learner error from clients with AutoSync enabled. https://github.com/etcd-io/etcd/blob/main/client/v3/client.go#L188 here does not exclude learner endpoint

What did you expect to happen?

Either requests are not sent to learner endpoints only or learner endpoints proxy requests to non learner member

How can we reproduce it (as minimally and precisely as possible)?

Add a new member but do not promote it, and wait for client autosync to pick the new member

Anything else we need to know?

No response

Etcd version (please run commands below)

etcdctl version: 3.5.0
API version: 3.5

Etcd configuration (command line flags or environment variables)

paste your configuration here

Etcd debug information (please run commands blow, feel free to obfuscate the IP address or FQDN in the output)

$ etcdctl member list -w table
# paste output here

$ etcdctl --endpoints=<member list> endpoint status -w table
# paste output here

Relevant log output

No response

[serathius]

There is a PR in flight #13837

[serathius]

Fix will be available in v3.5.3