Expose divertallemailsto and divertallemailsexcept in the admin settings GUI

1. Setup mail catcher or real email
2. In config.php set up some email diverting rules

   $CFG->divertallemailsto = 'your@email.com';

   $CFG->divertallemailsexcept = 'exception@email.com,.*example.com';

3. Confirm these are shown as normal settings here: YOUR_MOODLE_URL/admin/settings.php?section=outgoingmailconfig
4. Delete them from config.php and then set them manually from the admin page.
5. Test sending various emails using YOUR_MOODLE_URL/admin/testoutgoingmailconf.php and confirm the emails are diverted/not diverted as follows.

   Recipient	Email diverted?
   s1@hello.com	Yes
   exception@hello.com	Yes
   exception@email.com	No
   s1@example.com	No

Note: Diverted emails will have the word "DIVERTED" on their subject

1. Test that diversion rules also work by separating them with line breaks instead of commas.