Update etcd raft package to v3.3.27

[denis-gudim]

This PR provides the following changes for Raft consensus protocol service:

1. Removed dependencies to not up-gradable etcd module https://github.com/ConsenSys/etcd v3.3.13 and replaced to vanila https://github.com/etcd-io/etcd v3.3.27 version.
2. Moved changes by Quorum team from obsolete https://github.com/ConsenSys/etcd package to main repository (added required code only).
3. Added types compatibility between customized by quorum team and source raft packages
4. Added few minor changes to Raft consensus service source code

The main idea of this PR is to remove obsolete etcd package and provide ability to upgrade etcd package easier further.

[baptiste-b-pegasys]

cool great job

[CLAassistant]

All committers have signed the CLA.

[denis-gudim]

cool great job

thanks a lot
added small addition changes: restored etcd package structure in raft/etcd directory

[baptiste-b-pegasys]

Sorry for late answer.
I tested upgrade of node, and I managed to do it by updating all the nodes (stop/new image/start nodes) at once only.
I think for raft it is OK because it is dedicated for dev or test setups.

[denis-gudim]

Sorry for late answer. I tested upgrade of node, and I managed to do it by updating all the nodes (stop/new image/start nodes) at once only. I think for raft it is OK because it is dedicated for dev or test setups.

No problem. Thanks for your time