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/tree/modifiers/expand-all.lua

@@ -0,0 +1,80 @@
+local core = require "nvim-tree.core"
+local renderer = require "nvim-tree.renderer"
+local Iterator = require "nvim-tree.iterators.node-iterator"
+local notify = require "nvim-tree.notify"
+local lib = require "nvim-tree.lib"
+
+local M = {}
+
+---@param list string[]
+---@return table
+local function to_lookup_table(list)
+  local table = {}
+  for _, element in ipairs(list) do
+    table[element] = true
+  end
+
+  return table
+end
+
+---@param node Node
+local function expand(node)
+  node = lib.get_last_group_node(node)
+  node.open = true
+  if #node.nodes == 0 then
+    core.get_explorer():expand(node)
+  end
+end
+
+---@param expansion_count integer
+---@param node Node
+---@return boolean
+local function should_expand(expansion_count, node)
+  local should_halt = expansion_count >= M.MAX_FOLDER_DISCOVERY
+  local should_exclude = M.EXCLUDE[node.name]
+  return not should_halt and node.nodes and not node.open and not should_exclude
+end
+
+local function gen_iterator()
+  local expansion_count = 0
+
+  return function(parent)
+    if parent.parent and parent.nodes and not parent.open then
+      expansion_count = expansion_count + 1
+      expand(parent)
+    end
+
+    Iterator.builder(parent.nodes)
+      :hidden()
+      :applier(function(node)
+        if should_expand(expansion_count, node) then
+          expansion_count = expansion_count + 1
+          expand(node)
+        end
+      end)
+      :recursor(function(node)
+        return expansion_count < M.MAX_FOLDER_DISCOVERY and (node.group_next and { node.group_next } or (node.open and node.nodes))
+      end)
+      :iterate()
+
+    if expansion_count >= M.MAX_FOLDER_DISCOVERY then
+      return true
+    end
+  end
+end
+
+---@param base_node table
+function M.fn(base_node)
+  local node = base_node.nodes and base_node or core.get_explorer()
+  if gen_iterator()(node) then
+    notify.warn("expansion iteration was halted after " .. M.MAX_FOLDER_DISCOVERY .. " discovered folders")
+  end
+  renderer.draw()
+end
+
+function M.setup(opts)
+  M.MAX_FOLDER_DISCOVERY = opts.actions.expand_all.max_folder_discovery
+  M.EXCLUDE = to_lookup_table(opts.actions.expand_all.exclude)
+end
+
+return M