refactor: deprecate vim.region() #28416

Problem:
`vim.region()` is redundant with `getregionpos()`.

Solution:
Deprecate `vim.region()`.

runtime/lua/vim/_editor.lua

@@ -494,6 +494,7 @@ do
   vim.t = make_dict_accessor('t')
 end
 
+--- @deprecated
 --- Gets a dict of line segment ("chunk") positions for the region from `pos1` to `pos2`.
 ---
 --- Input and output positions are byte positions, (0,0)-indexed. "End of line" column
@@ -507,6 +508,8 @@ end
 ---@return table region Dict of the form `{linenr = {startcol,endcol}}`. `endcol` is exclusive, and
 ---whole lines are returned as `{startcol,endcol} = {0,-1}`.
 function vim.region(bufnr, pos1, pos2, regtype, inclusive)
+  vim.deprecate('vim.region', 'vim.fn.getregionpos()', '0.13')
+
   if not vim.api.nvim_buf_is_loaded(bufnr) then
     vim.fn.bufload(bufnr)
   end

runtime/lua/vim/lsp/buf.lua

@@ -135,7 +135,7 @@ end
 ---@param mode "v"|"V"
 ---@return table {start={row,col}, end={row,col}} using (1, 0) indexing
 local function range_from_selection(bufnr, mode)
-  -- TODO: Use `vim.region()` instead https://github.com/neovim/neovim/pull/13896
+  -- TODO: Use `vim.fn.getregionpos()` instead.
 
   -- [bufnum, lnum, col, off]; both row and column 1-indexed
   local start = vim.fn.getpos('v')