[TASK] Add iterable type to `PageErrorHandlerInterface::handlePageError`

The `PageErrorHandlerInterface` is often implemented in case a custom
error handler is used in site configuration. Static code analysis may
complain about missing iterable types in implementations. Thus, we now
provide the iterable types to ease the implementation effort in TYPO3
projects.

Resolves: #100004
Releases: main, 12.4
Change-Id: I9734ce09c091f6d0e6f68d19019e8d77d1ffc685
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79733


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>