Fixes:
go test -tags cluster_proxy ./clientv3/integration -v -run TestWatchRequestProgress
Does not fail the grpc-server (completely) by a not implemented RPC.
Failing whole server by remote request is anti-pattern and security
risk.
Prior to the fix, the command line above was failing with:
```
=== RUN TestWatchRequestProgress/0-watcher
panic: not implemented
goroutine 602 [running]:
go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxyStream).recvLoop(0xc0004779d0, 0x0, 0x0)
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:275 +0xac5
go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxy).Watch.func1(0xc0034f94a0, 0xc0004779d0)
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:129 +0x53
created by go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxy).Watch
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:127 +0x3c8
FAIL go.etcd.io/etcd/v3/clientv3/integration 0.215s
FAIL
```
grpc proxy opens additional 2 watching channels. The metric is shared
between etcd-server & grpc_proxy, so all assertions on number of open
watch channels need to take in consideration the additional "2"
channels.
Prior to the fix:
```
go test -mod=mod -timeout 30m -tags cluster_proxy "./integration/..."
```
Was failing with:
```
integration/cluster_proxy.go:58:37: not enough arguments in call to grpcproxy.NewWatchProxy
have (*clientv3.Client)
want (*zap.Logger, *clientv3.Client)
FAIL go.etcd.io/etcd/v3/integration [build failed]
```
This change makes the etcd package compatible with the existing Go
ecosystem for module versioning.
Used this tool to update package imports:
https://github.com/KSubedi/gomove
