[TASK] Custom error page: higher priority for class matches
All custom error rendering options should be evaluated for
matches of the exception class name before trying to match
against status code because the latter are often used as
fallback options (for example, 404 for anything not found).
The TYPO3.TYPO3 package wouldn't be able to display a specific
"Missing Homepage" error message without this patch because
FLOW3's 404 handling would kick in before.