clientv3: filter learner members during autosync

[chrisayoub]

This change is to ensure that all members returned during the client's
AutoSync are started and are not learners, which are not valid
etcd members to make requests to.

I have tested this patch with Kubernetes as a client and it works as intended.

[codecov-commenter]

Codecov Report

Merging #13837 (cc1b6fa) into main (4019c59) will decrease coverage by 0.17%.
The diff coverage is 100.00%.

❗ Current head cc1b6fa differs from pull request most recent head 125f3c3. Consider uploading reports for the commit 125f3c3 to get more accurate results

@@            Coverage Diff             @@
##             main   #13837      +/-   ##
==========================================
- Coverage   72.54%   72.37%   -0.18%     
==========================================
  Files         468      468              
  Lines       38222    38223       +1     
==========================================
- Hits        27730    27664      -66     
- Misses       8709     8763      +54     
- Partials     1783     1796      +13     

Flag	Coverage Δ
all	72.37% <100.00%> (-0.18%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
client/v3/client.go	80.89% <100.00%> (+2.29%)	⬆️
server/auth/simple_token.go	80.00% <0.00%> (-8.47%)	⬇️
client/pkg/v3/fileutil/lock_linux.go	72.22% <0.00%> (-8.34%)	⬇️
server/storage/mvcc/watchable_store.go	85.14% <0.00%> (-4.72%)	⬇️
server/storage/wal/file_pipeline.go	90.69% <0.00%> (-4.66%)	⬇️
server/etcdserver/api/v3rpc/watch.go	84.89% <0.00%> (-3.70%)	⬇️
api/etcdserverpb/raft_internal_stringer.go	76.78% <0.00%> (-3.58%)	⬇️
client/v3/leasing/txn.go	88.09% <0.00%> (-3.18%)	⬇️
server/etcdserver/util.go	85.71% <0.00%> (-3.18%)	⬇️
server/etcdserver/api/v3compactor/periodic.go	87.50% <0.00%> (-2.50%)	⬇️
... and 18 more

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[ahrtr]

LGTM

Thank you.

cc @serathius @ptabor @spzala

[chrisayoub]

@ahrtr it says First-time contributors need a maintainer to approve running workflows. I assume I need some sort of approval for this to merge?

[chrisayoub]

@serathius anything else we need here before merging?

[serathius]

Second maintainer approval. cc @ptabor @spzala

[spzala]

Thanks @chrisayoub
lgtm

[serathius]

Note, I think we should have an e2e tests with learners.