This PR adds support for ZeroMQ to listen on multiple interfaces, just like the RPC server.
Currently, if you specify more than one e.g. zmqpubhashblock paramter, only the first one will be used. Therefore a user may be forced to listen on all interfaces (e.g. zmqpubhashblock=0.0.0.0:28332), which can result in an increased attack surface.
With this PR a user can specify multiple interfaces to listen on, e.g.
-zmqpubhashblock=tcp://127.0.0.1:28332 -zmqpubhashblock=tcp://192.168.1.123:28332.
This is a backport of core#18309