vim-patch:9.0.0423: "for" and "while" not recognized after :vim9cmd and :legacy (#24825)

Problem:    "for" and "while" not recognized after :vim9cmd and :legacy.
            (Emanuele Torre)
Solution:   Recognize all the command modifiers. (closes vim/vim#11087)
            Add a test to check the list of modifiers.

9132426334

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

test/old/testdir/test_eval_stuff.vim

@@ -146,6 +146,15 @@ func Test_for_over_null_string()
   let &enc = save_enc
 endfunc
 
+func Test_for_with_modifier()
+  " this checks has_loop_cmd() works with a modifier
+  let result = []
+  horizontal for i in range(3)
+    call extend(result, [i])
+  endfor
+  call assert_equal([0, 1, 2], result)
+endfunc
+
 func Test_for_invalid_line_count()
   let lines =<< trim END
       111111111111111111111111 for line in ['one']