set_property to open/close a folder

[jwnimmer-tri]

In the context of RobotLocomotion/drake#20797, it would be helpful to allow programmatic remote control over the folder state.

One way to offer that would be a property message:

{
  "type": "set_property",
  "path": "/drake",
  "property": "folder_open",
  "value": true
}

When the value is true we'd call folder.open(), for false we'd call folder.close().