patch 8.2.4837: modifiers not simplified when timed out

Problem:    Modifiers not simplified when timed out or using feedkeys() with
            'n" flag.
Solution:   Adjust how mapped flag and timeout are used. (closes #10305)
diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index c9b0c7b..87c0474 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -2444,5 +2444,21 @@
   bw!
 endfunc
 
+func Test_simplify_noremap()
+  call feedkeys("i\<*C-M>", 'nx')
+  call assert_equal('', getline(1))
+  call assert_equal([0, 2, 1, 0, 1], getcurpos())
+  bw!
+endfunc
+
+func Test_simplify_timedout()
+  inoremap <C-M>a b
+  call feedkeys("i\<*C-M>", 'xt')
+  call assert_equal('', getline(1))
+  call assert_equal([0, 2, 1, 0, 1], getcurpos())
+  iunmap <C-M>a
+  bw!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab