fix(#2746): background and right aligned icons in floating windows (#3128)

* fix(#2746): fix cursorcolumn and right aligned icons in floating windows

* feat: remove right aligned icons from full name float, show float over right aligned icons

* refactoring: move `extmarks_length` to utils.lua

* fix: decrease `win_width` instead of increasing `text_width` when computing condition for full name float to show

---------

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

lua/nvim-tree/utils.lua

@@ -172,6 +172,21 @@ function M.find_node_line(node)
   return -1
 end
 
+---@param extmarks vim.api.keyset.get_extmark_item[] as per vim.api.nvim_buf_get_extmarks
+---@return number
+function M.extmarks_length(extmarks)
+  local length = 0
+  for _, extmark in ipairs(extmarks) do
+    local details = extmark[4]
+    if details and details.virt_text then
+      for _, text in ipairs(details.virt_text) do
+        length = length + vim.fn.strchars(text[1])
+      end
+    end
+  end
+  return length
+end
+
 -- get the node in the tree state depending on the absolute path of the node
 -- (grouped or hidden too)
 ---@param path string