vim-patch:8.1.0815: dialog for file changed outside of Vim not tested (#28184)

Problem:    Dialog for file changed outside of Vim not tested.
Solution:   Add a test.  Move FileChangedShell test.  Add 'L' flag to
            feedkeys().

5e66b42aae

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/eval.lua

@@ -2481,6 +2481,7 @@ M.funcs = {
       't'	Handle keys as if typed; otherwise they are handled as
       	if coming from a mapping.  This matters for undo,
       	opening folds, etc.
+      'L'	Lowlevel input.  Other flags are not used.
       'i'	Insert the string instead of appending (see above).
       'x'	Execute commands until typeahead is empty.  This is
       	similar to using ":normal!".  You can call feedkeys()