Move node classes to node module

lua/nvim-tree/node.lua

@@ -0,0 +1,33 @@
+---@meta
+
+---@class ParentNode
+---@field name string
+
+---@class BaseNode
+---@field absolute_path string
+---@field executable boolean
+---@field fs_stat uv_fs_t
+---@field git_status GitStatus|nil
+---@field hidden boolean
+---@field name string
+---@field parent DirNode
+---@field type string
+---@field watcher function|nil
+
+---@class DirNode: BaseNode
+---@field has_children boolean
+---@field group_next Node|nil
+---@field nodes Node[]
+---@field open boolean
+
+---@class FileNode: BaseNode
+---@field extension string
+
+---@class SymlinkDirNode: DirNode
+---@field links_to string
+
+---@class SymlinkFileNode: DirNode
+---@field links_to string
+
+---@alias SymlinkNode SymlinkDirNode|SymlinkFileNode
+---@alias Node ParentNode|DirNode|FileNode|SymlinkNode