revocation: Don't merge auth config of CLR/OCSP trustchain validation

revocation: Don't merge auth config of CLR/OCSP trustchain validation

This behavior was introduced with 6840a6fb to avoid key/signature strength
checking for the revocation trustchain as we do it for end entity certificates.
Unfortunately this breaks CA constraint checking under certain conditions, as
we merge additional intermediate/CA certificates to the auth config.

As key/signature strength checking of the revocation trustchain is a rather
exotic requirement we drop support for that to properly enforce CA constraints.