feat(pos): create a cursor position by using the current of a window

Problem:
`vim.pos.cursor(vim.api.nvim_get_current_buf(win), vim.api.nvim_win_get_cursor(win))`
is too verbose to create a cursor position of a window,
but it is a common use case.

Solution:
Overload `vim.pos.cursor()`, so that it accepts `win` as an argument when `pos` is omitted.

runtime/lua/vim/lsp/util.lua

@@ -1810,10 +1810,9 @@ end
 ---@see https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocumentPositionParams
 function M.make_position_params(win, position_encoding)
   win = win or 0
-  local buf = api.nvim_win_get_buf(win)
   return {
-    textDocument = M.make_text_document_params(buf),
-    position = vim.pos.cursor(buf, api.nvim_win_get_cursor(win)):to_lsp(position_encoding),
+    textDocument = M.make_text_document_params(api.nvim_win_get_buf(win)),
+    position = vim.pos.cursor(win):to_lsp(position_encoding),
   }
 end