patch 9.1.0349: Vim9: need static type for typealias

Problem:  Vim9: need static type for typealias
Solution: Refactor the typval2type() function and add a static type for
          typealias (Yegappan Lakshmanan)

closes: #14582

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 442d375..7737cce 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -4783,6 +4783,8 @@
   if has('channel')
     assert_equal('channel', test_null_channel()->typename())
   endif
+  assert_equal('class<Unknown>', typename(null_class))
+  assert_equal('object<Unknown>', typename(null_object))
 enddef
 
 def Test_undofile()