[BUGFIX] Provide lang and uc data for workspace notification localization

The notification e-mails of workspace changes need the lang of the
BackendUser record, this change introduces the lang and uc fields
in the getBackendUsers-method to enable the right localization of
notifications.

Releases: master, 8.7
Resolves: #46217
Change-Id: I45991fa7ef1a5d3610da5f16c5f363aa1f697611
Reviewed-on: https://review.typo3.org/53294


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Thomas Hohn <thomas@hohn.dk>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>