Motivation is as follows:
- etcdctl we only depend on clientv3 APIs, no dependencies of bolt, backend, mvcc, file-layout
- etcdctl can be officially supported across wide range of versions, while etcdutl is pretty specific to file format at particular version.
it's step towards desired modules layout, documented in: https://etcd.io/docs/next/dev-internal/modules/
So far each instance of embed server was overriding the grpc loggers and zap.global loggers.
It's counter intutitive that last created Embedded server was 'wining' and more-over it was breaking grpc expectation to change it "only" before the grpc stack is being used.
This PR introduces explicit call: `embed.Config::SetupGlobalLoggers()`, that changes the loggers where requested. The call is used by etcd main binary.
The immediate benefit from this change is reduction of test flakiness, as there were flakes due to not a proper logger being used across tests.
Thanks to this, unix sockets should be not longer
created by integration tests in the the source code directory,
so potentially trigger IDE reloads and unnecessery load (and mess).
"snapshot" Restore/Status code was the only remaining dependency of client on 'server'
code. The code is solelly used by etcdctl. Long-term the snapshot code
should be migrated to 'etcdadm' style of tool such that we can
distinguish tool solelly depending on networking API vs. tools that
operation on etcd files directly.
We left snapshot.Save() code in clientv3.snapshot package, such that
clients can benefits from automated download&safe to file snapshot
functionality over the wire.
