[FEATURE] Add hreflang support

This feature adds an hreflang tag for multilanguage-websites (one-tree)
automatically, based on the new LanguageMenuProcessor.

The href is relative as long as the domain is the same.
If the domain differs the href become absolute.
x-default href is the first supported language.

Resolves: #75806
Releases: master
Change-Id: I06754f61d7a03f6894001be11c9ce2a37ac2106f
Reviewed-on: https://review.typo3.org/58105


Reviewed-by: Richard Haeser <richard@maxserv.com>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>