runtime(vim): Update base-syntax, improve :augroup highlighting (#14125)

- Explicitly match the bang and group name in :aug! {name}.
- Allow any characters in a group name.
- Match default group switch marker, END.
- Match :aug without arguments (list command).

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

runtime/syntax/testdir/input/vim_ex_augroup.vim

@@ -0,0 +1,19 @@
+" Vim :augroup command
+
+augroup foo
+  autocmd BufRead * echomsg "Foo"
+augroup END
+
+augroup foo | autocmd! | augroup END
+augroup! foo
+
+augroup !@#$%^&*()_+
+  autocmd BufRead * echomsg "Foo"
+augroup END
+
+augroup !@#$%^&*()_+ | autocmd! | augroup END
+augroup! !@#$%^&*()_+
+
+" list groups
+augroup
+