We would like to discourage and disconnect peers that send us messages
with invalid netmagic and checksums (D1234 and D2289)
To do that after core#19107 I could either 1. make BanMan globally
accessible 2. pass it into the needed scope via new function parameters
or 3. pop the control flow out to where it is accessible using exceptions.
This implements option 3.
Depends on D12956