Improve CLI logout flow (#1692)

* Improve CLI logout flow

* Fix lint error

* Make notLoggedInMessage a const

* successful logout with a msg when cfg files are absent

* use require, os.remove, show only one message, add prompt

cli/userlist_test.go

@@ -14,6 +14,7 @@ import (
 )
 
 func TestUserList(t *testing.T) {
+	t.Parallel()
 	t.Run("List", func(t *testing.T) {
 		t.Parallel()
 		client := coderdtest.New(t, nil)