Also add explanation in `EditorContextMenuPlugin`'s doc for fixing path information passing
(Accept PR #106820 suggestion by: Tomasz Chabora <kobewi4e@gmail.com>)
As there are multiple menu containing creating new files, this commit add the popup menu item from the plugin to all those menu to keep consistency.
The fixing uses empty array to indicate different types of context menu.
Added to these menu:
* Right-click on empty space on the tree (`_tree_empty_click`).
* Right-click on empty space on the file panel (`_file_list_empty_clicked`)
Also add explanation in `EditorContextMenuPlugin::CONTEXT_SLOT_FILESYSTEM_CREATE`'s doc for previous fixing
(Accept PR #106811 code suggestion by: Tomasz Chabora <kobewi4e@gmail.com>)
