patch 8.2.2941: Vim9: using  does not handle a list of strings

Problem:    Vim9: using  does not handle a list of strings.
Solution:   Convert a list to a string and escape each item. (closes #8310)
diff --git a/src/testdir/test_vim9_cmd.vim b/src/testdir/test_vim9_cmd.vim
index 87832ce..6b31a62 100644
--- a/src/testdir/test_vim9_cmd.vim
+++ b/src/testdir/test_vim9_cmd.vim
@@ -34,6 +34,10 @@
 
   CheckDefFailure(['edit `=xxx`'], 'E1001:')
   CheckDefFailure(['edit `="foo"'], 'E1083:')
+
+  var files = ['file 1', 'file%2', 'file# 3']
+  args `=files`
+  assert_equal(files, argv())
 enddef
 
 def Test_expand_alternate_file()