* refactor(#2942): multi instance: move find_node_line to Explorer
* refactor(#2942): multi instance: move get_node_from_path to Explorer
* refactor(#2942): multi instance: move focus_file to Explorer
* refactor(#2942): multi instance: move focus_node_or_parent to Explorer
* refactor(#2942): multi instance: move get_node_from_path to Explorer
* refactor(#2942): multi instance: move find_node to Explorer
* refactor(#2942): multi instance: move get_nodes_by_line to Explorer
* refactor(#2942): multi instance: remove unnecessary focus_file
* refactor(#2942): style