runtime(vim): Improve Vim9 and legacy-script comment highlighting (#13104)

This is a first-pass attempt to limit matching of Vim9 and legacy-script
comments to the appropriate syntactic contexts.

Vim9-script comments are highlighted at top level in a Vim9-script file,
in all :def functions, and in all :autocmd and :commmand command blocks.
Legacy-script comments are highlighted at top level in a legacy script
file, in all :func functions and in the Vim9-script preamble before the
:vim9script marker command.

Fixes #13047, #11307 and #9587.

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/generator/gen_syntax_vim.vim

@@ -3,7 +3,7 @@
 " Maintainer: Hirohito Higashi (h_east)
 " URL: https://github.com/vim-jp/syntax-vim-ex
 " Last Change: 2024 Apr 07
-" Version: 2.1.0
+" Version: 2.1.1
 
 let s:keepcpo= &cpo
 set cpo&vim
@@ -286,6 +286,7 @@ function! s:get_vim_command_type(cmd_name)
 	\	'append', 'insert',
 	\	'Next', 'Print', 'X',
 	\	'new', 'popup',
+	\	'vim9script',
 	\ ]
 	" Required for original behavior
 	" \	'global', 'vglobal'