feat(ssh+cli): Support SSH CLI on machine init and add commands (#173)

* Add SSHCLIRemote type with buildSSHArgs

Implement's Executor interface (Run, Stream, Close)

* Add UseSSHCLI field to RemoteMachine struct

Allow us to differentiate regular ssh from ssh+cli.

* Parse ssh+cli:// scheme on machine init/add

* Support SSH CLI when provisioning

* Update docs to reflect ssh+cli:// support

* Revert removal of `init` examples

Fixes copy & pasta mistake when documenting the new ssh+cli connection
methods.

internal/cli/machine.go

@@ -21,10 +21,11 @@ const (
 )
 
 type RemoteMachine struct {
-	User    string
-	Host    string
-	Port    int
-	KeyPath string
+	User      string
+	Host      string
+	Port      int
+	KeyPath   string
+	UseSSHCLI bool // indicates ssh+cli:// should be used
 }
 
 func installCmd(user string, version string) string {