etcdctl: support progress notify option

[jingyih]

Add --progress-notify to etcdctl watch command. Example output:

$ etcdctl watch foo --progress-notify
progress notify: 1272
progress notify: 1789
progress notify: 2001
progress notify: 2001
...

[codecov-io]

Codecov Report

Merging #11462 into master will decrease coverage by 0.26%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master   #11462      +/-   ##
==========================================
- Coverage   64.21%   63.95%   -0.27%     
==========================================
  Files         403      403              
  Lines       38079    38082       +3     
==========================================
- Hits        24453    24354      -99     
- Misses      11993    12096     +103     
+ Partials     1633     1632       -1

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/watch_command.go	44.08% <33.33%> (-0.18%)	⬇️
pkg/transport/timeout_conn.go	60% <0%> (-20%)	⬇️
auth/jwt.go	58.09% <0%> (-10.48%)	⬇️
auth/store.go	45.66% <0%> (-7.79%)	⬇️
pkg/netutil/netutil.go	63.11% <0%> (-7.38%)	⬇️
clientv3/leasing/util.go	91.66% <0%> (-6.67%)	⬇️
clientv3/concurrency/mutex.go	62.16% <0%> (-5.41%)	⬇️
pkg/logutil/zap_grpc.go	47.61% <0%> (-4.77%)	⬇️
clientv3/leasing/txn.go	88.09% <0%> (-3.18%)	⬇️
proxy/grpcproxy/watch.go	89.94% <0%> (-2.96%)	⬇️
... and 14 more

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[spzala]

Thanks @jingyih LGTM Also, couple of observations - requires changelog updates, and wondering if we should support this in 3.3 as well.

[xiang90]

lgtm. can you add change log?

[jingyih]

wondering if we should support this in 3.3 as well.

I think generally we do not want to backport a new flag.

[jingyih]

CHANGELOG updated in the same PR. PTAL.

[spzala]

wondering if we should support this in 3.3 as well.

I think generally we do not want to backport a new flag.

OK, that's fair. Thanks @jingyih LGTM.

[spzala]

Merging as @xiang90 also had lgtm earlier :)