vim-patch:9.0.1688: cannot store custom data in quickfix list (#24673)

Problem: cannot store custom data in quickfix list
Solution: add `user_data` field for the quickfix list

closes: vim/vim#11818

ca6ac99077

Co-authored-by: Tom Praschan <13141438+tom-anders@users.noreply.github.com>

runtime/lua/vim/_meta/vimfn.lua

@@ -3309,6 +3309,9 @@ function vim.fn.getpos(expr) end
 ---   text  description of the error
 ---   type  type of the error, 'E', '1', etc.
 ---   valid  |TRUE|: recognized error message
+---   user_data
+---     custom data associated with the item, can be
+---     any type.
 ---
 --- When there is no error list or it's empty, an empty list is
 --- returned. Quickfix list entries with a non-existing buffer
@@ -7595,6 +7598,9 @@ function vim.fn.setpos(expr, list) end
 ---     text  description of the error
 ---     type  single-character error type, 'E', 'W', etc.
 ---     valid  recognized error message
+---     user_data
+---     custom data associated with the item, can be
+---     any type.
 ---
 --- The "col", "vcol", "nr", "type" and "text" entries are
 --- optional.  Either "lnum" or "pattern" entry can be used to