[BUGFIX] Make external page error handling work again

In recent TYPO3 v11.5.x versions, the error handling for Frontend
pages did cache the external PSR-7 Response (by guzzle) in the
pages cache. However, if the error page was fetched the second time,
the Response object from the cache did not have a valid stream anymore,
thus resulting in an array.

This change now caches the body + headers for the page (still, only
when a 200 response code was returned), and re-builds a clean Response
object.

Resolves: #95940
Related: #95586
Related: #94402
Releases: master
Change-Id: I27aaffe8acda275fd3450f9479e19a3f21d22df6
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72184


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>