patch 9.1.1405: tests: no test for mapping with special keys in session file

Problem:  tests: no test for mapping with special keys in session file.
Solution: Add a special keys to an existing test.  Also test with UTF-8
          characters containing 0x80 or 0x9b bytes (zeertzjq).

closes: #17360

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index 72a9376..bbb42f9 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -1153,10 +1153,10 @@
 func Test_mkvimrc()
   let entries = [
         \ ['', 'nothing', '<Nop>'],
-        \ ['n', 'normal', 'NORMAL'],
-        \ ['v', 'visual', 'VISUAL'],
-        \ ['s', 'select', 'SELECT'],
-        \ ['x', 'visualonly', 'VISUALONLY'],
+        \ ['n', 'normal', 'NORMAL<Up>'],
+        \ ['v', 'visual', 'VISUAL<S-Down>'],
+        \ ['s', 'select', 'SELECT<C-Left>'],
+        \ ['x', 'visualonly', 'VISUALONLY<M-Right>'],
         \ ['o', 'operator', 'OPERATOR'],
         \ ['i', 'insert', 'INSERT'],
         \ ['l', 'lang', 'LANG'],