runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups (#14137)

* runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups

- Remove contained :syntax and :highlight sub-groups from the function
  body cluster.  These should only match in the respective commands.
- Remove vimSynLine syntax group from several clusters.  The definition
  of vimSynLine was removed in Vim 5.3.

* runtime(vim): Update syntax generator, use standard Last Change date format

The de facto standard date format is YYYY MMM DD.

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

runtime/syntax/testdir/input/vim_ex_syntax.vim

@@ -162,3 +162,16 @@ syn keyword testKeyword
       \ keyword5
       \ keyword6
 
+
+" leaking contained groups
+
+" Example: runtime/syntax/zsh.vim
+"   "cluster" should not be highlighted outside of :syntax commands
+
+function! s:ContainedGroup()
+  " ...
+  for cluster in ['markdownHighlight_zsh', 'zsh']
+    " ...
+  endfor
+  " ...
+endfunction