Automatic merge from submit-queue (batch tested with PRs 41331, 45591, 45600, 45176, 45658)
Move client/unversioned/remotecommand to client-go
Module remotecommand originally part of kubernetes/pkg/client/unversioned was moved
to client-go/tools, and will be used as authoritative in kubectl, e2e and other places.
Module remotecommand relies on util/exec module which was copied to client-go/pkg/util