clientv3: simplify grpc dialer usage.

[YoyinZyc]

fix #11519
verified by tests under tests/docker-dns, tests/dorker-dns-srv, tests/docker-static-ip
@jpbetz @gyuho

[codecov-io]

Codecov Report

Merging #11574 into master will decrease coverage by 0.79%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #11574     +/-   ##
=========================================
- Coverage   64.57%   63.78%   -0.8%     
=========================================
  Files         403      403             
  Lines       38097    38074     -23     
=========================================
- Hits        24600    24284    -316     
- Misses      11851    12130    +279     
- Partials     1646     1660     +14

Impacted Files	Coverage Δ
clientv3/client.go	71.67% <ø> (-2.75%)	⬇️
clientv3/balancer/resolver/endpoint/endpoint.go	81.89% <100%> (-2.46%)	⬇️
clientv3/credentials/credentials.go	84.61% <100%> (+1%)	⬆️
clientv3/ordering/kv.go	33.82% <0%> (-51.48%)	⬇️
auth/simple_token.go	63.41% <0%> (-23.58%)	⬇️
client/keys.go	68.34% <0%> (-23.12%)	⬇️
auth/store.go	51.02% <0%> (-17.35%)	⬇️
clientv3/namespace/watch.go	87.87% <0%> (-6.07%)	⬇️
clientv3/concurrency/mutex.go	62.16% <0%> (-5.41%)	⬇️
etcdserver/api/v3rpc/lease.go	64.77% <0%> (-4.55%)	⬇️
... and 19 more

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[xiang90]

There are a few exposed public method removed. Will this affect client API backward compatibility?

[YoyinZyc]

There are a few exposed public method removed. Will this affect client API backward compatibility?

Most of them are the workaround from #11184. We can safely remove them after bumping into latest gRPC.

[gyuho]

lgtm, can we highlight this fix in CHANGELOG 3.5? thx

[YoyinZyc]

lgtm, can we highlight this fix in CHANGELOG 3.5? thx

Sure. Will do after merged.