cli: Improve error handling for plugin commands (#24250)

* Stop supporting vault plugin info and deregister without a type argument
* Make a best-effort attempt to report whether a plugin was actually deregistered and give more descriptive errors
* Fix error message for vault plugin reload

command/plugin_info_test.go

@@ -34,6 +34,12 @@ func TestPluginInfoCommand_Run(t *testing.T) {
 		out  string
 		code int
 	}{
+		{
+			"not_enough_args",
+			[]string{"foo"},
+			"Not enough arguments",
+			1,
+		},
 		{
 			"too_many_args",
 			[]string{"foo", "bar", "fizz"},