Move ban checking from WCF boot to middleware

Move ban checking from WCF boot to middleware

The previous location in WCF made sense back when `initBlacklist()` also
checked the IP address, User-Agent, or hostname blocklist to prevent processing
the request as much as possible. As all these checks are gone now, the only
thing that remains is the inexpensive ban check.

Move it into a middleware, it does not really belong into WCF which should just
be responsible for booting the framework independently of the request in
question.