refactor: improve API readability and tidy actions submodules (#2593)

* refactor: improve API readability, tidy actions modules

* Apply requested changes

* `actions/reloaders/reloaders.lua` -> `actions/reloaders.lua`

---------

Co-authored-by: Alexander Courtis <alex@courtis.org>

lua/nvim-tree/actions/moves/init.lua

@@ -0,0 +1,7 @@
+local M = {}
+
+M.item = require "nvim-tree.actions.moves.item"
+M.parent = require "nvim-tree.actions.moves.parent"
+M.sibling = require "nvim-tree.actions.moves.sibling"
+
+return M