Bug 36148: Allow Koha::Middleware::CSRF to use error/exception middlewares

Bug 36148: Allow Koha::Middleware::CSRF to use error/exception middlewares

This change allows Koha::Middleware::CSRF to use the ErrorDocument and
HTTPExcetions middlewares to display the correct status codes and HTML
documents.

Leveraging Plack environmental variables, we're also able to pass along
data to the error page handlers to show warnings indicating that there
was a missing CSRF token.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>