Fix a couple of issues with state change emails in
workspaces:

* We still can't deep link to the backend. The generated
  comparisonLink to the side-by-side preview module is a
  workspace backend functionality. The generated links
  don't work and show the login form. The fix is to
  generate "preview links" instead which call a frontend.
  We may be able to improve this later, when core v11
  allows deep linking.

* When changing the stage of a page delete placeholder
  - when a page is for deletion in live - preview link
  generation to these pages does not make sense, trying
  to generate such a link throws an exception "no
  connection to page tree", the ajax request fails and
  no mails are send. Fix is to catch the exception and
  leave out the link in the emails.

* Preview links did not carry the language id when
  sending notifications for state changes of non default
  language records. This is added to properly link to
  non-default language previews.

* A missing closing p-tag in the HTML mail.

* As a better default, preview links are now always added
  to the mails if possible. In rare cases where this is
  not wanted, the mail templates should be adapted.

Change-Id: I84f0e4e5131d52ecbc5e7424137ae7e2ebdb2031
Resolves: #91515
Resolves: #81708
Related: #90411
Releases: master, 10.4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67342


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>