[WIP][FAB-18363] Update Protobuf to 1.4.3

[lindluni]

Need to sort through the orderer/consensus/etcdraft issues yet and anything that comes out of integration tests as I haven't run them locally yet (doing it now).

Also: Yes, I will squash once I'm done

[lindluni]

Likely blocked due to this: etcd-io/etcd#12398 (comment)

More info here: etcd-io/etcd#12124

[lindluni]

It seems there are two issues at play here:

1. etcd doesn't support grpc > 1.29
2. etcd still uses gogo/protobuf which doesn't support the 1.4 protobuf standard
3. etcd needs to release the 3.5-alpha.0 build to deal with module issues they have (likely won't happen before the end of the year)

This blocks the upgrade of many of our dependencies unless we do some hacky things in our go.mod to pin our deps to a version that etcd doesn't use, and then do a replace on their versions to something they support.