[BUGFIX] PSR-7 responses return header using getHeader()

The base PSR-7 implementation of the Response object does not
sanitize the headers properly when handing them in as an array,
thus, it is stored wrong in the Response object.

Resolves: #84853
Releases: master, 8.7
Change-Id: I7571f1438bc602bcae9367b82f99946ed22d8308
Reviewed-on: https://review.typo3.org/56093


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Wolf <andreas.wolf@typo3.org>
Tested-by: Andreas Wolf <andreas.wolf@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>