[BUGFIX] Only include translated pages in sitemap

When generating the list of pages for a sitemap in
an alternative language only pages are considered that
are actually translated or covered by the fallback
strategy.

Additionally the method generateItems() in the internal
class PagesXmlSitemapDataProvider is now protected.

Resolves: #90046
Releases: master, 9.5
Change-Id: I54557e0485ae7791ac51fa975991d6d9c9211b61
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62865


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Richard Haeser <richard@maxserv.com>