util: Introduce virTypedParameterRemote datatype

util: Introduce virTypedParameterRemote datatype

Both admin and remote protocols define their own types
(remote_typed_param vs admin_typed_param). Because of the naming convention,
admin typed params wouldn't be able to reuse the serialization/deserialization
methods, which are tailored for use by remote protocol, even if those method
were exported properly. In that case, introduce a new internal data type
structurally copying both admin and remote protocols which, eventually, would
allow serializer and deserializer to be used in a more generic way.