fix(diagnostic): setqflist() is stuck after vim.lsp.buf.document_symbol #31553

Previously, when updating the quickfix diagnostics list, we'd update it,
and then open the quickfix buffer, but there was no guarantee that the
quickfix buffer would be displaying the quickfix diagnostics list (it
could very possibly be displaying some other quickfix list!).

This fixes things so we first select the quickfix list before opening the
quickfix buffer. If `open` is not specified, the behavior is the same as
before: we update the diagnostics quickfix list, but do not navigate to
it.

fixes https://github.com/neovim/neovim/issues/31540

runtime/lua/vim/diagnostic.lua

@@ -869,7 +869,16 @@ local function set_list(loclist, opts)
     })
   end
   if open then
-    api.nvim_command(loclist and 'lwindow' or 'botright cwindow')
+    if loclist then
+      api.nvim_command('lwindow')
+    else
+      -- First navigate to the diagnostics quickfix list.
+      local nr = vim.fn.getqflist({ id = _qf_id, nr = 0 }).nr
+      api.nvim_command(nr .. 'chistory')
+
+      -- Now open the quickfix list.
+      api.nvim_command('botright cwindow')
+    end
   end
 end